> Quinn decided that he, (Quinn) wasn't a murderer and that he killed "bad guys". Brody had fulfilled his part of the bargain and didn't deserve to be killed. I think :/
Precisely. Quinn was having doubts about killing Brody even at the end of the previous episode. It wasn't just because he saw him praying that he stopped. Quinn's a good guy.
> Who else knew the bomb vest was in the car? Or was it another bomb?
I suspect it was another bomb, on the grounds that no sane person drives around with that much explosive in their car for months. Also with the places he was visiting, you'd think his car would be regularly checked for explosives (e.g. by sniffer dogs). Also the bomb seemed way too big for a vest bomb - not that I'm an expert in these matters, but when you hear of such atrocities on the news, car bombs can kill on the scale of the attack last night, whereas vest bombs seem to kill on a smaller scale. (Lovely topic for Christmas Eve!)
> And just before Nazir was shot, did he touch something on his chest?
He reached inside his clothing in order to get himself shot. It was a means of avoiding being captured alive. He knew they'd have to shoot him if he made as if to reach for a weapon or a bomb trigger.