I know this isn't helpful now - but the best thing would have been to avoid allowing the baby to nurse to sleep from the beginning. My advice to friends is always - don't do it now if you don't want to be doing it a year from now. (Like a poster said below - if you are fine with the practice, more power to you. But if its a problem, that is what my response is based on.) Now that your baby is already used to nursing to sleep, it is probably almost impossible to get rid of all that nursing without some crying. That doesn't mean you have to "cry it out" though.
I would try reading "healthy sleep habits, happy child." It has four different methods, not just cry it out. You could try the elimination method. With that one you put the baby to sleep in their bed, and come back to soothe every 10, 15 minutes, etc. It will probably be a hard few weeks, but hopefully it will work.
On one other note, I don't think babies are ready to cry it out at 5 months old anyway. So I wouldn't go that route yet even if you were open to it.
Hopefully if he was in a crib without you, the pacifier might become more attractive to him. Lastly, I think that is really interesting that your DR said he needs the food since he is big. Mine have always said the other way around - with that much weight they should be able to sleep through the night no problem.