I have a few suggestions, you should work more on a very good logo , I recommend contacting SFR10[1] as he is a very good designer and his prices are good , you should also consider adding a favicon.
Website design looks very clean and good but categories are someting to definitely expand , you should consider adding Wordpress themes and plugins etc... in Webmaster and ability to sell serial keys in "Software" too.

Gaming section in the other hand should contain "Steam gifts/keys" , "Origin keys" , "Battle.net keys" etc... In addiction to CS:GO accounts and skins and whatever you already added.
Picture on the bottom of the page (SIGN UP now and start selling) is not clickable while It definitely should be.
Finally , I think that you should let users buy without the need of registering but you should give them a warning that they won't be able to use the escrow system in that case.

[1] https://bitcointalk.org/index.php?action=profile;u=521899

Its probably going to be successful and in the first hours only , I mean they have over 150 million registered users worldwide and the fact that he kept the users database and he is going to leave it and give premium membership for those who already had it means he actually cares and Its not a matter of money only for him.
We probably don't have enough details about Bitcache and how Its going to work with bitcoin and micro payments but I'm sure he knows what he is doing.

Slut.io is no longer functional , they changed the domain a few months back to Selly.io (which is the selly.gg that I mentioned above) and they don't really sell anything , Its up to you to sell whatever you want there (as long as Its digital goods).

I never heard of it before but after doing some googling I suppose Its BTC/USDT and It available in Poloniex (with the highest trading volume) , Bitfinex , Bittrex and C-CEX and see here for more details : https://coinmarketcap.com/assets/tether/#markets

Everything should be available to read from their official blog : https://blog.openbazaar.org/ and there is definitely weekly improvements since the first day they released it . Unless they keep developing it and start doing some serious marketing and advertising the software even though Its decentralized , It will end up dead for sure.

As shown on coinmarketcap markets : https://coinmarketcap.com/currencies/sync/#markets Its not possible to trade it anywhere else . If they indeed removed it then Its worthless and I doubt anyone would want to buy it.

I don't see much people posting in that thread so I doubt Its anything serious. It has been reported that they have some issues in the last few hours too https://status.coinbase.com/ and their trading volume is nothing compared to the other exchanges , so even If they got hacked as claimed , I doubt It was the reason for this price decrease.

I really suggest that everyone holds what he have at the moment instead of panic selling , If you want to really make some really good profit then hold . http://preev.com/ , Its not going too well and we don't want to make things worst at this point.

People are already in panic and started to sell , I can't say that this wasn't expected though. Hopefully the weak hands will sell and the holder will keep holding for long term.

Satoshibox only allow uploading files and selling them https://satoshibox.com/ while others allow multiple things such as accounts etc... even though you probably can't upload a file , you still can put a think from an external website and the user will get it whenever he pays. See https://selly.gg/ and https://rocketr.net/
All of them are legit and reputable as far as I know and I've never seen a scam accusation against any of them.

Its not recommended by them , bitcoin.org adds the wallet as long as they meet the requirements. As for your issue then I'm almost sure that Its because of your browser , have you tried to change the browser ? or clear your cache and cookies and try again.

Its definitely a weird issue , are you sure you are not using a 2FA wallet thats asks you for the 2FA code instead of the password Itself ?
If you have the seed as you said then I suggest upgrading to the latest version (If you didn't already) restoring the wallet and adding another password instead. If the problem persists then open a github issue on Electrum repository.

Its all based on supply and demand and I don't see how It could fall to 0$ just like that but If you mean , It will be cheap as hell then I will put my feelings aside and I will start buying , I feel like I don't have enough BTC to make a lot of profit at the moement.
But to be realistic a little bit , I doubt this is a scenario that could happen ,It could've happened a few years back when no one knew about bitcoin but now ? very unlikely.

Website is functional but they are having a lot of problems , you should check the status page : https://status.coinbase.com/ you will find all info whenever there is an issue on the platform.

Its a wallet indeed but they have a Local Trader built inside the application. It uses your location (GPS) to detect the nearest sellers and buyers that you could meet and trade with. I personally find meeting face to face a little bit risky and also doesn't give you fully anonymity as the other party will see your face. Details : https://mycelium.com/lt/help.html

Its a multi signature wallet , giving you the ability to control both private keys wouldn't make any sense , nothing is stored in their servers as well so even If they get hacked there is nothing to be worried about.
If it ever happens and the service goes down for one reason or another then you could recover it[1][2] using the documents they gave you when you first installed the wallet.

[1] https://recovery.blocktrail.com/
[2] https://github.com/blocktrail/wallet-recovery-tool (Source code of the website above)

Its not like the funds of users has been stolen (at least not that I'm aware of) and bitcoin network has nothing to do with it , Its related to their website and their security procedures.
You should definitely think twice about storing your bitcoin into a bitcoin website (exchange or online wallet). Its never safe.

"Fiat money is currency that a government has declared to be legal tender, but it is not backed by a physical commodity. The value of fiat money is derived from the relationship between supply and demand rather than the value of the material that the money is made of" -- Investopedia

So basically fiat value is based on supply and demand and same thing for bitcoin as well , the higher demand it is , the better. I doubt we will see changes in fiat just because of bitcoin demand only though , at least not in the next few years.

It says "We're sorry, but the company you are looking for does not exist." and just because the employee profiles are made in public doesn't mean Its legit honestly unless they are known and used by multiple people. Have you used them yourself?

I've seen someone advertising for this http://bitcoinchart.io/ but I never tried it because It requires downloading and I'm too afraid to do it. From the way It looks , I have to say Its a well done job but I want to know what are your feedbacks and reviews about it before I get it on my PC.