Jessica--
I don't know if I would worry so much about the naps, they say a well rested child sleeps better at night. If you did, maybe just by an hour or 1 1/2 hours at most. Are his naps consolidated, or are they catnaps through the day? Consolidated sleeping is supposed to help. Also, is it full on crying, or just whining/mantra crying at night? If you ignore it for a few minutes, what happens? This never worked with my son, he just threw himself into a frenzy, but it did help with my daughter as she was able to settle herself.
Something else I read on another post: babies at this age are becoming more alert and aware. You could start making A time a little more stimulating--not longer, but different. Sit him up, play little games, sing songs, take him outside (of course, with our great NW weather you may have to wait on that! :? )--it may wear him out more so he rests better at night.
I know you don't want to do the dream feed, but it does take hunger out of the question of why he's waking. My son is also a big boy, we df at 10:30 and he is able to go until about 6-7 in the morning. He maybe wakes once a night (unless he's sick/teething--then it's about twice), but it's solved just by giving him his paci.
Now, one other thing I do that has helped (he used to get up several times a night), is put him on his tummy to sleep. On his back he would kick his legs in the air, flail his arms all around and get himself riled. On his tummy he's less mobile. Now I know some people don't like tummy sleeping, but I don't worry since he's able to pick up his head so easily.
Anyway, I'll stop the rambling. Just wanted to shoot out a few ideas!
HTH
Melissa