Every mom and every child are different. You need to decide what both you and your child can deal with, but you must keep the end result in mind. What do you want? Do you want your son to co-sleep for a bit more, or do you want him to be able to fall asleep on his own?
If you want him to fall asleep on his own, I would suggest moving his crib into his own room, and establishing a concrete bedtime routing (bath, book, bed). If the CIO method is not working, or is making both of you crazy than modify it a bit.
I bought the "No Cry Sleep Solution" book. After three days of following its suggestions (go in after 3 mins, 5 mins, 7 mins, 10 mins etc)...my son was absolutely petrified of not only sleeping, but of his crib and room as well!!
So, I threw all of that out the window and did my own little thing. I basically went in stages, once we passed one stage (consistently falling asleep for 3 days in a row) we moved onto the next. Stage 1: he was in the crib, I was next to him rubbing his back, talking to him. Stage 2: he was in crib, I was next to him only talking to him, no rubbing his back. Stage 3: he was in the crib, I was standing next to the crib, no rubbing no talking. Stage 4: he was in the crib, I was in the glider across the room, occasionally talking to him. Stage 5: he was in the crib, I was in the glider silent. Stage 6: he was in the crib, I was in the doorway occasionally talking to him. Stage 7: he was in the crib, I was in the doorway silent. Stage 8: he was in the crib I was out of sight, but would occasionally talk to him. Stage 9: he went to sleep completely on his own.
For us, this was a long process - about 6-8 weeks, but it worked. And all of that work is sooooooo worth it in the end.
Any time anyone visits, they comment on how shocked they are at our nap/bedtime routine. No problems at all now!!!!
Again, this is definitely the long route, but when all else fails, it is an option.
Good luck!