If your cold-storage set-up isn't new or after using it once:
You need to always get a receiving address from the online watch-only wallet to be sure that the one you get isn't already used.
The offline wallet can't know which addresses was used so it might display the same address in the 'receive' tab over and over again.
(guessing you already know the privacy implications of reusing addresses)

The whole post including the title is unclear,
is there an issue when you created a transaction or are you trying to create a transaction that has a custom change address?

Also, that first part seems like an entirely different issue.
If you mean the address in the receive tab, that's normal when you've already used the "actual address";
Electrum will give you a new address after the previous one was used, but it's still in your wallet and useable if you wish to.

I think I get where your confusion with the total is.
In "Johoe's Bitcoin Mempool Statistics", the numbers you see in each fee rate range is already the total of the ones on top of each range.
So for example, the value in "1+" is the total size of all transactions from 1~2000+ in the graph.

What's been weird in the site since the update is the seemingly stuck <1sat/vB transactions when you enable to 0+ minimum flag.
But we're getting out of topic, you can start a new thread if you want to continue the discussion about that specific mempool statistic site.

You almost got the name, it was "Change Address" not "Exchange Address"  

It works like that because an "unspent transaction output" (UTXO) needs to be spent whole, a part of its value can't just be deducted.
Once a UTXO was spent, it can't be used again, that's why the excess amount should be a new UTXO (the change) or it will be considered as transaction fee.
Read this: https://en.bitcoin.it/wiki/Transaction#Output

I noticed that too.
With the updated version, when you try to force the minimum to 0, you'll see that there are a lot of accumulating
<1sat/B transaction in his mempool: jochen-hoenicke.de/queue/#BTC,3m,weight,0

But based from this: /jhoenicke/mempool/blob/master/web/queue/mempool.js
He's using the default mempool setting so there shouldn't be any <1sat/B txn in his mempool, it must be a bug in the site or server.

Some parts are readable, you can try it on your wallet.dat with transaction history, a copy of course.
But since some contains too many lines, you may have to use a text editor that can handle thousands of lines of text.

This will only work if those wallets were used before, I mean, displayed the final balance the last time they were used:

• Create a copy of each wallet so you wont mess around the originals.
• Then open each of the copy wallet.dat using a text editor.
• Using the search function (CTRL+F), find all lines with name, and a Bitcoin address should be next to it.
• Check its balance using a blockexplorer.

Note: If the wallet wasn't fully synced before, it may or may not display the funded addresses in the text editor.
So loading them to a fully synced Bitcoin core is still the best solution.

If you have more than one large inputs and the amount you want to send only requires one for example, using the custom change wont send all of your remaining balance to the specified change address, only the remaining amount from the used input.
If you want to send all of the remaining balance from Bitcoin core to Electrum, just add it as a new recipient ("+ Add Recipient" button below) and click "Use available balance" once you've filled up the other outputs.

When you click the 'add recipient' button, another "pay To" field will be generated, if your Bitcoin core's window is small, you'll have to use the scroll on the right to see the second payTo field.

Electrum's seed isn't BIP39 compliant, the developers used their own mnemonic seed phrase implementation:
electrum.readthedocs.io/en/latest/seedphrase

That will work;
the error he'll get is just a warning about the BIP39 checksum below the seed: BIP39 (checksum: failed) but the next button will is still be available.

But I wouldn't suggest that since it's a non-standard way of creating an HD p2sh-segwit wallet.
It'll force Electrum to get an entropy from the Electrum seed phrase that will be used as BIP39 seed.
Downloading an offline copy of iancoleman's BIP39 tool is easy, it's open-source and the current code is clean.

The linked thread is quite outdated since it's for older versions of Electrum.
Following step 7 will produce a different set of keys for BIP49 derivation path.
Instead of manually editing the path, all he has to do is to select p2sh-segwit (p2wpkh-p2sh) in the Script type and Derivation path window of the later Electrum versions.

Wait! You said "addresses".
Have you successfully created an [imported] Electrum wallet, not an [imported, watching-only] wallet?
Check the wallet's name in Electrum's title bar.

Or do you mean you've copy/paste all the "private keys"?
If yes, then it's all good.

That's because of Electrum's current behavior when importing private keys:

• If there's no prefix, it will import the private key into P2PKH whether it's WIF compressed or not.
• If there's a prefix, it will follow that prefix's script type.
• For SegWit (P2WPKH / P2WPKH-P2SH), it wont take uncompressed WIF private key because using uncompressed WIF prvKey in SegWit is non-standard.

Converting the WIF keys to compressed surprisingly works (not for P2SH-P2PK, only for P2SH-P2WPKH),
Armory will display the uncompressed WIF key when exporting a P2WPKH-P2SH address' keys (which is wrong IMO), but able to derive the correct nested SegWit address based from the compressed public key.
Maybe that's the reason why that option is grayed-out when selecting an address type in the GUI of v0.96.5.

Is this an answer to the OP or your own question?

If the it's a question, please include more info about the issue so people can help you better, better if you open a new thread.
If it's your answer, the earlier posts already have more info about what the WIF private key looks like.

Yup, there are settings that won't trigger the issue and I haven't tested them all.
What works at my end are the ones listed in my original reply, any one of the three.
I've also noticed that once a setting inactivated the max button, it won't do it again the second time unless Electrum restart.

I believe that's not the issue, it originated in the 'send' tab's "max" button so, he just have to click "Max" and then "Pay..." without doing anything in between that can deactivate the max toggle.

Actually, I expected more but you have a point. So the reason is not technical then.

---

@OP / Others, In case you're looking for help, I strongly suggest you to follow the second post instead; and please ignore any PMs offering "services" or "help".

I have reproduced this by changing something in the setting that'll make max button non-highlighted.
That makes the displayed to-be-sent value an absolute amount (not affected by 'max'), so changing the fee will produce a change.

Here's what I've done:

• Put an address in the send tab, click "Max". Max will be highlighted indicating that it's active.
• Go to "Tools->Preferences", Untick/Tick something under 'transactions' tab. I've tried 'RBF', 'output rounding' and 'change address'.
• When you close the preferences window, the max button will be inactive but the previous amount will stay. So it'll act as a manually input amount instead of the auto adjusting max amount.

I don't know if there are other factors that can untoggled the max button but you must have done something that untoggled it before you clicked the send button.

You've reinstalled Core so the issue must be in the data directory.
There are couple of issues that could cause, "Error opening Block database" but since you have just disabled pruning,
it won't hurt to start with a clean blocks directory to sync from scratch. It will sync from start after disabling pruning anyways.

Find Bitcoin's data directory, the default is: C:\Users\Drake\AppData\Roaming\Bitcoin (Shortcut: WinKey+R | Enter %appdata% | open "Bitcoin" folder)
I've included your username since it's already in the logs.
Create a backup of that folder (for safety) and delete "blocks", "chainstate" and "index" folders inside the original.
While you're at it, double-check the bitcoin.conf file (open with txt editor) if you still have any pruning settings enabled, all must be disabled.

Run Bitcoin core and it should sync from start (see if pruning is still ticked in the GUI).

Electrum v4.0.4 [Oct. 15, 2020] has a "Cancel (double-spend)" option in the right-click menu of an RBF flagged transaction.
That's basically the same as "increase fee" but instead of sending to the same output(s), the wallet will send it back to the owner's wallet.

Those addresses under "used" in Bitcoin wallets are addresses that received bitcoin at least once and should belong to your HD wallet while I'm not sure if 6-8years old blockchain.info wallets are non-HD.
Anyways, the balance of 'used' addresses should reflect to your total balance but it didn't.

Based from your conversation with the customer support, specially about the xPub, it seems like it's not covered by the master public key and erroneously included to the default wallet.
From that, your wallet itself might be missing the private key for that address so I doubt that you can find the keys using the export wallet file method.
If you want to try it, here are the steps:

• Export your wallet file (wallet.aes.json), use btcrecover to download it: https://github.com/3rdIteration/btcrecover/releases
  That's a command line tool and requires Python, the tool you need is download-blockchain-wallet.py inside "extract-scripts" folder.
  Watch the video tutorial by BTCRecover (from start to 3:50): https://www.youtube.com/watch?v=eS0VUl3w69Y to see how to use the tool.
• And decrypt it using blockchain's offline decryption tool: https://github.com/blockchain/my-wallet-backup-decryption-tool/releases
  It's easy to use since it has a GUI, you just have to browse to the wallet.aes.json file and type your password. But make sure to use this in an offline PC to be safe.

Note: the private keys will be displayed in "Base58" and you wont be able to use it to other wallets, you can use brainwallet's converter to convert it to "WIF" = Wallet Import Format (Base58Check) to be able to import the key to another wallet.
I'd suggest you to use the offline version to be safe: https://github.com/brainwalletX/brainwalletX.github.io | Code->Download Zip | Extract it and open index.html on an offline PC's browser.
Go to "Converter" tab, Select "Base58" in the 'Source Encoding' and "B58Check" in the 'Convert to', then paste the Base58 private key to the Source text, the WIF private key will be displayed in the result.
You can import it to Electrum (https://electrum.org/#download | verify its signature) using a new wallet option: "Import bitcoin addresses or private keys".

That's quite a long process... but if there's no private key for the address, try to export the master private key (xprv) instead in the backup decryption tool's button "View JSON".
That can be imported to Electrum using these new wallet options: "Standard->Use a master key".

Other than those, I have no other suggestion.