Here's a guide I put together with a collection of helpful links and tools. It has some of those answers and also some useful tools.

1. Yes, keep posting, commenting, upvoting and resteeming other people's posts.

2. From what I've heard, it's both dollars and steem-based dollars (sbd) in a way. There's a peg between a dollar and steem or SBD, I can't remember which.

3. https://steemit.com/steemit/@penguinpablo/here-s-why-your-potential-payouts-are-going-down

4. See the guide on that too.

5. When you upvote, you'll end up making a share of what that post or comment makes. It's most often quite small and paid in steem power. The more you upvote, the less your vote will be worth. Your voting power does recharge, though it takes awhile.