[Micah]

I believe 2 is a yes, based on Rlyeh's insanity allowing multi-prophets. I think the prophet command is available 6 months after you don't control any prophets, as opposed to tracking unit number. I may be mistaken.

Upkeep is almost certainly the current controller's problem.

I believe RoR is targetted based on the nationality they're filed under in the HoF, so you should be able to Rebirth them if they died under your control.

No idea on 1 and 5. I'm really surprised they'd lose priest levels from that, actually.