1. I think only one channel can be bridged, yes. I was told by my installer when I got my last sound system that bridging a mutli channel amp is bad for the connections. I'm not sure on wires.
2.
http://www.alpine-usa.com/product/view/sbr-s8-4 Thats what I found on alpine, seems to suit your needs and then some. Not sure if its too much, but I cant imagine a 8" woofer with a sealed box wouldn't be much different.
assuming thats #3, I had kenwood speakers in my doors, 6'5s all around. The previous speakers were infinities, but they were self installed by the previous owner and no filters were put in so it sounded like crap.
http://www.alpine-usa.com/product/view/spe-6000 These look like good door speakers? hah I like alpine stuff, they're bulletproof stuff.
__________________
"Ah! What music! They could have never imagined, those pioneers who invented the automobile, that it would posses us like this, our imaginations, our dreams. Men love women, but even more than that, men love CARS!"-Lord Hesketh