I know how hard this is, to hear them cry at night, to not get any sleep and know that you have to function the next day, to feel so brutal...
but it is actually harder on him that you give in. if you stick to your guns and don't nurse no matter what he does, he will eventually fall back to sleep. And he'll learn that it isn't worth it to get up. Keep a bottle of water so he can feel liquid in his throat after crying so much. But keep the boobs in the jammies.
I'm going through this, too, and it is really hard. But kids look for patterns in behavior. That is how they learn. If the pattern is "I'll cry till I turn blue then I'll get what I want," then you are teaching him to cry. If the pattern (totally consistantly) is, "I cry and cry and still no breast," He'll stop crying after a few days b/c it just doesn't work.
I'm night weaning my ever hour nursing 18 month old. I'm right there with you and after 2 hours of sleep last night, I feel your pain! We can do it, though. Good luck!
EDIT: I am not a proponent of leaving a baby in his/ her crib to cry for a long time. I would be TERRIFIED if that were me in the crib, wondering where the person who cares for me has disappeared to! My baby sleeps with me, so when he cries, I snuggle him. I know he feels safe and secure. The only thing I'm willing to take away from him is the breast.