Sending durood upon Nabi (sallallahu alaihi wasallam)

Q: I have a friend and his mom asked him, as she is jahil, is it permissible to send darood on Nabi Muhammad (sallallahu alaihi wasallam) and he said I don't know with respect because he thought that it may be shirk and then he said"Lekin kiya zaroorat he" with respect not with niyyat of disrespect. He said this because he thought it means that we are maybe asking from Nabi Muhammad (sallallahu alaihi wasallam) or something. Is this kufr?

Meaning of "one salaah time passing" for a person to be a ma'zoor

Q: I would like to find out about being azoor with regards to flatulence. I believe you qualify if you pass wind during one salah time.

My question is, does the salah time mean from the beginning of a certain salah i.e. fajr upto Zuhr start, or just the amount of time between wudu and completion of fajr salah? Also, between Isha and fajr it is a very long time. Does the rule still apply at that time. Please clarify.