Following along in the order of your questions:
- Nope, no fee's, just a wallet.
- This does not replace an exchange like bittrex - there's no trading in the wallet (yet?).
- The chain would end up being Vessel -> Exchange -> Bank Account. You don't have to move funds to the wallet, you just import your keys into the wallet and now you can use your Steem account from it (instead of the website). Using Vessel means you no longer have to rely on your web browsers security and entering your master password or active keys into it.
- I don't know enough about gumroad to answer your question - but the wallet can be used for users to send Steem to eachother.
- Vessel could accept other cryptocurrencies (and act like a wallet), but it's not an exchange to trade within.
No worries about the crazy comment - more than happy to help with the learning :D
Thank you for answering my questions. I thought of a few more but decided not to post them here. I'll continue to follow and read the chainbb forum. I'll catch on.