3/ INTCON.0 = 1 changes to INTCON.0 = 0 (software reset)
INTCON.0 will only "=1" when one of the IOC pins change state. The code makes sure the "trigger" is set before sleeping. I think you got that though.

5/ @ NOP (I'll take as per NOP above, I couldn't find anything on this in the manual).
No Operation... I am here but I ain't doing nothing.
Look to the data sheet under Instruction Set Summary. The ASM instructions are found there.

Looks like you have been studying