Okay, let me try to answer all of this real quick.
1) If you're not on the payment list, wait a bit. We review writers for each round prior to finalizing earnings (so if you aren't on it yet, you may still get on it before the round is finalized -- we do all these checks at once)
2) Technically, the round "ends" in a few days. Due to tying up loose ends and ensuring everything is right, though, it drags on past that. Usually up to a week.
Basically, until the actual payment files ("receiver files") are uploaded, things are not finalized.
Yep, there is a period after the round to correct errors, et cetera.