ItcheSrulik:
1) R Chaim in pesachim (somewhere within the first few blott of the second perek; sorry I don’t remember were)
6) I won’t be able to give you a makor for that sorry. I was talking to my dad about this who told me the various times to wait for Motzei shabbos (72,92,1/8 of the day 1/6 of the day). I asked him if anyone actually keeps 1/6, and he said maybe some really radical briskers do.
8) As a result of this, some briskers don’t wear tzitzit on shabbat (see the ba’al hamor and ramban commenting on the ba’al hamor who paskens like the tanna kamma in menachos 38a (i think the ba’al hamor is somewere in mesachet shabbat though) and the rashi to eruvin 73b to see why). My dad said the funniest were the people who didn’t wear tzitzit but were somech on the eruv for other things