I can't answer all the questions, but I'll answer what I can. I was out on short-term disability, but with sick leave it was a total of six months. Long term (depending on how long, but isn't that long if you have a Surface 2) might be different.
1) Three weeks or so to get back in the sim from when I told the doc I was ok. I had a straight-forward back surgery, so the Delta doc gave me the OK to return to work in a matter of hours. Don't expect that he will linger over your case. I had no input, but had about a week notice of the sim. When you're feeling better, start studying. I was scheduled for a "Special Equal". Essentially it was a two day CQ plus an extra day on the front end. The Captain I had was another guy going through Requal from another airplane.
1b. It went smooth, but not a lot of room for error or not knowing what you're doing. The flying does come back quickly though - I was off six months, got sick right after sim training. I had never flown the airplane (no OE) when I went to the special requal.
2b. The training section in the FOM (part 2) has the details, but it's hard to understand. Just call the Chief Pilot center and they'll send you to the right people.
2c. I got a reserve line, but they either ask you what days you want off, or give you weekends, I can't remember. You can move them around afterward with PCS.
2d. You get the leftovers, yes. But be aware, you aren't earning any vacation while out (LT might be different), so you might not have any vacation to bid.
3) I think if you are out less than 36 months you get a short course for re-training.
4) No idea.
5) There was no academic class in Atlanta. You have to complete the last 4 CQ disks, so you'll learn it there. But the study was really on your own.
6) No idea about FAA leave, depends if the TA passes and when they implement the FAA leave.