1. The p35 board is a better overclocker and can be used for a potential penryn upgrade in the future. It has a fantastic reputation, too. The 965p is a good board, too, it's just very outdated. You could buy the 965p board and get an e4500, but you'll probably get the same final oc out of the p35/e4400 combo as you would out of the 965p/4500 combo. Also, the e4500 isn't even out yet and you would bust your budget going up to e6550.
2. The prices just dropped today on intel chips. The e4400 is faster and has a better multiplier.
3. What games are you playing? What monitor/resolution? The 7900 gs could be fine, or it could be terrible. ATI and nvidia are both supposed to come out with more mid-range type cards in the next few months so you might try to get by with your current card for a few months and see what pops up.