What I believe from experience and info gathered from Veteran players over the years..
1) Troops that safely entered the map room will stay alive until the field is captured , Town ack pops or Town Flag pops.
2) Common belief is YES. if you up again, your troops no longer count as being in map room. How ever, I personally don't believe this to be the case.
I believe once a troop has entered the map room uninjured, that troop counts regaurdless of whatever happens.
3) NO, straffing maproom has no effect on troops that have already entered. either does bombing it.
4) YES, the guns popping resets the maproom.