Dietcokegirl, have you tried staying with him in his room until he falls asleep, and then withdrawing?
I had similar to you, in that dd1 was a fab sleeper when she was little. it took unitl she was 4ish before it all went ot pot, and then boy, did it all go to pot!
we ended up having t stay with her unitl she slept - all low key, no contact, no engagement. first of all on the bed with her, then next to the bed then a little further away, etc. slowly, slowly. it didn't take long for us to be able to withdraw to the doorway of her room, but we did then get a little stuck.
but still, we had a structure and a plan, and tried ot keep chipping away at it. thank god for laptops! as I could work/MN/watch films etc while sitting there.
it has been a very long slow road for us, but finally, we do now put the girls to bed (they share a room) and come downstairs - dd1 is now 6.5.
the htign that helped me most wrt losing it, was the fact we had a plan. we knew what we were doing/where we were aiming. we worked, cm by cm, towards a goal. and once a stage had been achieved (ie outside the doorway, rather than inside the doorway) we didn't go back (unless an emergency, of course). we were, at the same time, working on getting the bedroom door closed too, and millimetre by millimetre we woudl close it a fraction more each night/week/whatever.
the aim was to get dd1 to the point of not-coping, but never tip her over the edge - always to go just as far as she coudl cope with. if she lost it, and we had to comfort her, that was a backward step. but by pushing her boundaries whenever we could, we taught her how to check things were ok (eg she owuld come to the door of the room to see we were still there) and to deal with her emotions.
re: sweets/rewards. you don't have to use sweets, or even edible rewards. dd1's current reinforcers are me patting her chest, or me telling her the time/talking about the time/clocks. use whatever is most rewarding for your ds - a word you say, a game you play; tickles; time on the computer (when possible); a favourite dvd was the reward/reinforcement for dd1 when she was toilet training - she had to do whatever stage she had got to (and we broke it right down into touching the door then opening the door, going inside the bathroom, sitting on the loo seat with lid closed and fully clothed, etc etc) before she got to watch a snippet of her would-kill-for dvd.