question on castle storming

[Merry Jolkar]

I have three questions regarding the timing of castle storming. Forgive me if these are addressed elsewhere-- I think the situation is special enough that it may be novel.

I have a force sieging a castle. The enemy still has a single soldier (not a commander) in the castle at least according to the battle record from Last turn's failed effort to storm the castle (all commanders retreated). I also have forces in two adjacet provinces. The enemy has a large force in another province adjacent to the castle.

1) If I storm with the force already seiging the castle, will they enter the castle and have an opportunity to kill the sole remaining soldier before his forces can come to the rescue? (In which case, I suppose that soldier, being leaderless, would flee, right?)

2) If he and I both send our forces from adjacent provinces, will we fight outside the castle, or will the forces friendly to the castle enter the castle and help defend it?

3) If my current sieging forces can expunge the one soldier left defending, and he moves in, does he then wind up sieging?

Thanks!
Merry