You're asking a lot of questions here... I'll try to answer a couple of them, but i'd suggest you try to read up on the concept of hard forks and soft forks.
Basically, during a hard fork, part of the network starts to use incompatible consensus rules that are enforced starting at a certain block height.

In other words: up untill block x, both sides of the fork have exactly the same data in their public ledger, simply because part of the network chose to follow different rules starting at block x.
This means that, if you have an unspent output that funds an address controlled by your wallet, and the funding transaction is confirmed before block height x, the transaction is included in a block before the hardfork. This means that after block height x (after the hardfork), the unspent output is spendable on BOTH sides of the fork.

In other words: if you have 1 BTC pre-hardfork, you'll have 1 BTC and 1 alt-BTC you can BOTH spend post-fork.

However, if the group of people that caused the hardfork didn't implement replay protection, a transaction spending a pre-fork unspent output on one chain, can be replayed on the forked chain... There are ways around this problem, but that's a completely different question.

There are dozens of threads detailing what will happen then. Just use the search function:
https://cse.google.com/cse?cx=016660200577587308545%3Aesf40ml9aag&ie=UTF-8&q=after+all+bitcoin+mined&sa=Google+search#gsc.tab=0&gsc.q=after%20all%20bitcoin%20mined&gsc.page=1

Actually, it's not 100% true that in the end there will be 21 million BTC in circulation:
https://en.bitcoin.it/wiki/Controlled_supply

Look at the table in the link i posted:
by block 6930000, the block reward will be 0.00000000, at this point,    20999999.97690000 BTC will be brought into circulation.

Bitcoin is decentralised... There are no system interruptions.
If a node goes down, it doesn't matter, dozens of other people are still running full nodes
If a miner goes down, even a big one, worst case scenario there is a 10% hashrate drop, so it the average time between two blocks would be 660 seconds instead of 600 seconds untill the next diff retarget.

Bitcoin isn't bound by country borders... A transaction is always broadcasted troughout the network of nodes in a matter of seconds (unless there is something wrong with the transaction, like double spent inputs, dust outputs, a fee that is so low the tx gets rejected by some nodes,...). Wether or not the broadcasted transaction ends up in a block in a  reasonable timeframe depends on the fee.

A transaction is alway broadcasted in a matter of seconds... It's possible the transaction remains unconfirmed for a while if the sender cheaped out on the fees.

At this moment, the recommanded fee to have a 95% chance of getting into the next 3 blocks is 110 sat/byte. This is still reasonable. It has been lower, but it certainly has been higher: https://bitcoinfees.21.co/

In other words: the people making excuses saying that there is a transaction delay are not telling the truth... If they need to fund one of your addresses, they can do so in a matter of seconds, and if they didn't cheap out on the fee, their transactions will be confirmed in less than 30 minutes (on average).

Allmost
1: in electrum wallet -> view -> show coins
2: open coins tab
3: check if deposit address has unspent outputs (coins)
4: if true, ctrl-click on the unspent outputs, select them all -> right click -> spend (fund an address generated by a new, clean, encrypted wallet). If false skip to step 6
5: wait untill tx from step 4 is confirmed
6: In Electrum wallet : Wallet ->Private keys - > export
7: save the exported file on my desktop.
8: locate the private key belonging to the address you wrongfully funded on the Bitcoincash network, copy this private key
9: download a Bitcoincash wallet, for example electroncash (but other wallets work as well)
10: open electroncash, generate a new wallet using a PRIVATE KEY (not a seed)
11: paste the private key from step 8 in the wizard's interface in due time
12: spend the output on the bitcoincash network
13: clean up everything (as soon as the tx from step 12 is confirmed, delete the electroncash wallet, delete the file from step 7,...)
14: In Electrum wallet : Addresses->Right click -> Freeze
14b: even better, create a new wallet, generate a new deposit address, go to the old wallet, click on send, paste the new deposit wallet and click on "max" (empty out the old wallet). Don't use the compromised wallet again (if possible). This last step is an alternative for step 14 in case you're a paranoid person (like me)

Export the private key corresponding to the funded address from your BTC-electrum
import this private key into a bitcoin cash wallet (depening on the wallet, a rescan might be needed)

Mark the BTC address in electrum as compromised, never use it again. It might even be wise to empty the BTC-electrum wallet and stop using it.

EDIT: i forgot: before exporting the private key for the deposit address from electrum, make sure there are no unspent outputs on the bitcoin network funding this address... If there are, it might be wise to spend these outputs on the bitcoin network before exporting the private key from electrum and importing it in an bitcoincash wallet... Bitcoincash wallets seem to be pretty secure, so the chance of them exposing the private keey are minimal, but it's better to be safe than sorry!

I have no idear... I've had tokens that did have a price attached to them in the past, so they probably either have a minimum bidding price, or they're following a specific exchange, or there is a manual intervention from etherscan... I haven't taken the time to read their FAQ yet

To the miner that included your transaction into the block he/she was trying to solve (and succeeded in solving + broadcasting said block)

Etherscan shows a total sum of all your tokens  in FIAT
For example, my tokens are currently worth a whopping $0 
https://etherscan.io/address/0xd65400079adaba8cccad4f3d20d21f13b6240514#tokentxns

20-25 characters long?

An encrypted private keys is 58 characters and starts with a "6"
A private key in WIF format is 51 characters and starts with a "5"
A WIF compressed pk is 52 characters and starts with 'K' or 'L'
A pk in hexadecimal format is 64 characters long
a pk base64 is 44 characters long

The only private key format that is 22 characters long seems to be
https://en.bitcoin.it/wiki/Mini_private_key_format => a variant of the minikey format

I don't think electrum supports this format. If you want to import a private key in this format, you should find a client that supports it... Unless that character sequence you have there isn't a private key at all...

The fork has occured... There is no need to refrain from using your bitcoin wallet wallet... But if want to claim your Bitcoingold, it might be a good idear to split your coins before actively spending BTC (this way it's easyer to track your unspent outputs on both chains).
The fork happened at blockheight 491407,  at the time of writing, we're at blockheight 491488 (bitcoin blockchain), so the fork happened 81 blocks ago

How?
Create a new BITCOIN wallet, empty out your old wallet by creating a transaction using all unspent outputs controlled by your old wallet to fund a deposit address on your new wallet.
AFTER this transaction confirmed on the bitcoin network, export your private keys from electrum and import them into a bitcoingold wallet. If, after a potential rescan (depending on which BCG wallet you use, i don't know which wallets exist), the balance remains 0, it means the transaction on the bitcoin blockchain must have been replayed. you have to start over.
If there is a balance in your BCG wallet, you can deposit these funds to the deposit address of your account on an exchange and exchange your BTC for a non-premined coin .

When?
I wouldn't know. Whenever you think it's the best time to maximise your profit?

This private key of yours, how does it look?
How many characters?
Which letter does it start with?

PS: only answer those two questions, do not share the private key with anybody... Don't even share a partial private key, or a blurred out picture!

So many replies, and nobody gave you the advice you really need to hear (IMHO).

Everything stands and falls with your electricity price. It doesn't matter if you're investing $0,5M or $5000... If you pay to much for your power, you're not going to mine BTC profitably.
If you're willing to dip your toe into altocoin mining, i'm told the electricity price can be a tad higher and you'll still be able to turn a profit, but don't expect to ROI quickly if you're paying 20 cents/kwu, even if you're altcoin mining. For me, the maximum power price to even think about mining BTC would be around 10 cents/Kwu. You can still mine with little higher prices, but the ROI gets to long (IMHO) and with the rising diff and the short guarantee of ASIC's, i'd personally not take the risk.

Offcourse, with a bankrol of $0,5M you have a little bit of leverage with your local power company, or you'll be able to get a better deal when you're looking for hosting in a datacenter, but $0,5M isn't sufficient to build your own datacenter and really put a vice on the power company when negotiating... So you're still at their mercy to get a good deal.

Before you decide anything, ask yourself the following questions:
- Will you be mining from home? If yes, how much does your power cost, do you have a suitable mining room, can you place A/C units, how's your wiring, what about security, what about fire hazards,...

- If you won't mine from home, all these factors will be taken care off by the hosting provider, but he'll add those (hidden) costs to your final bill, and there is a chance you pay more than you'd pay if you did everything yourself (so it would take a bite out of your profits).

If you wait untill you have a problem, it's usually to late 
I'd recommand to at least switch to a desktop wallet on a properly secured/clean pc, at least you'll be in controll of your own private keys, so you have nobody to blame but yourself if you mess up...

Nope, don't mix bitcoins and dollars.
The fee you pay has nothing to do with the value (in BTC) and certainly not with the transferred FIAT value (if you convert BTC to USD).

You pay a fee per byte of transaction data.
The size of a transaction is related to the amount of inputs and the amount of outputs. It does not matter if you use 10 inputs of 1  BTC/piece or 10 inputs of 0.0001 BTC/piece, the size is allmost the same because both transactions use 10 inputs.

The formula for calculating the size used to be:
tx size =~ nr of inputs*147 + nr of outputs*34 + 10 + number of inputs

Offcourse, nowadays, if you use a segwit wallet, the rules have changed a little bit, but the basic idear remains the same.

What kind of a guarantee?
MtGox was a big exchange, people are still trying to get any recompensation from them...
Bittrex is just locking accounts and keeping funds hostage...
Yobit simply disables wallets and doesn't answer tickets for weeks...
There are many big exchanges that have screwed over their users in the past. Don't think that your funds are safe just because the echange is big.

A laptop usually doesn't have a very good GPU, so you're more or less bound to cpu minable altcoins... They do exist, but most of them aren't worth much.
Also, a laptop usually doesn't handle a large load for a long time as well as a desktop usually does, so the chance of damaging your laptop by CPU mining is larger than CPU mining on a desktop.