Getting 13 month old * back* to sleep

I'm trying to move from co-sleeping with my 13 month old son to having him sleep in a crib. He's always awakened several times a night and I nursed him back to sleep, but I feel like I've created a bit of a monster! He is still waking so often, and nursing for what feels like hours (although I doze but uncomfortably).

I've put a mattress on the floor beside his crib and am doing the nightime routine. He cries a bit but within 15 minutes or so he's wound down and sleeping. But, when he wakes in the middle of the night, it's awful! Last night he stood and cried for 2 hours! If I try to leave the room, he screams bloody murder. I've tried different things, take him out and nurse him, then put him back, or don't take him out at all and see if he winds down, but no good results. I've tried talking reassuringly, not talking, etc.

I really want to minimize his discomfort, I'm not into the crying it out method, but I am desperate to get over the hump and get closer to good night sleeps for both of us. I'd really appreciate anyone's suggestions! Thanks so much!