Hi T. -
I can tell you what worked for us, having just "deswaddled" our daughter (4 months old) this week. So far so good, she's waking during the night just as much as she did when she was swaddled (2 times). In fact, it's been easier to get her to go back to sleep, because I think she was spending so much time wiggling out that it was waking her up. Anyway.....
1. Try letting him nap without the swaddle, so he can at least get used to the idea of going down without it. Our daughter's naps are pretty short/erratic, so for us, there wasn't too much to lose here.
2. We have her sleep in a sleep sack so that her legs are still bundled up as they would be in the swaddle. For naps, we wrap her in her swaddle blanket from the hips down.
3. When we put her to sleep, we put her down and give her 5 minutes to fuss it out a bit. Then we pick her up, rock her for 5 minutes to soothe her, then put her back in the crib. We let her fuss for 5 minutes (maybe putting our hand on her and ssshing her). If that doesn't work, we pick her back and up and repeat the 5 minute routine. This was suggested by our pedi as a sort of modified sleep training (since she's too young to really cry it out)
4. We put up her crib bumpers (I know they say not to use them because of SIDS, but at this point, we feel like our daughter can semi roll/turn her head) and we put her in a corner, so that her head is making contact with the bumpers. The pedi suggested that this can help her feel more secure vs. being along in the middle of the crib.
The first night that we put her down unswaddled, she looked at us like "Something's missing!" and fussed a bit. Last night we put her down and she didn't fuss at all, so it only took a couple of nights. Hopefully some of the suggestions will work for you - I know every child is different so you have to experiment and see what works. Good luck!