Bundle question - Steam/Desura

Yep, it will still work. They're independent.

They do. However, if it's Indie Royale, the key is the same for all the game and it gives anyone the link to your personal page. Don't give that one out until you've redeemed all Steam keys. (If you've got a Desura account, I think it automatically goes on it too unless you ask for a gift link.)