Must Hamapil be said at the begining or end of Kriyas Shma? And after saying Hamapil, how long are you prohibited from speaking until? And what kind of emergencies allow you to break this prohibition?
Major Machlokes Haposkim to the order. See the Aruch Hashulchan for talking.
The Sefas Emes Sidur places “Birkas haMapil” at the commencement to accommodate the possibility that one may drift into sleep before end of the various Piyutim accompanying Kerias Shema Al haMitah.
What does the Aruch Hashulchan say about talking? And which other poskim take a position on when one must stop talking until the morning? Btw, if you wake up in middle of the night can you talk? Walk? Eat?
I don’t remember perfectly, but I believe the Tzitz Eliezer agrees with the Aruch Hashulchan that even for a relatively minor bother you can talk and do things after the Brachah. The reason for this is because it’s not a Brachah on sleep itself, but a Birchas Hoda’ah on Minhago Shel Olam. The Mishnah B’rurah says not to. This makes sense because it lines up with their Machlokes about Hama’avir Sheinah (and Elokai Neshama) when one didn’t sleep. The Minhag recently (as evidenced on Shavuos) seems to, at the very least, be Choshesh for the M”B Lechatchilah. It also makes sense, since the M”B is seemingly in a minority in this, that the Aruch Hashulchan is perfectly fine to rely upon if it’s too much trouble.
If one slept a half-hour, you would be able to get up and do normal things, but you would have to wash Netilas Yadayim first.