Hi!
I hope this finds you well. I am sorry to hear about the sleep issues you are having, but don't worry. Things will work themselves out and you'll find what works for you and your son.
I'm not sure if I understood correctly, but does your son sleep with you and then you switch him to a crib? If so, how would you feel keeping him in bed with you the whole night? Would he still wake up as much? Have you tried putting his crib in your room?
With my daughter, who is now 22-months' old, I have always found that following my gut, no matter what anyone says, is what works best. I've done her sleep in stages based on what I felt she needed and made her most comfortable--first co-sleeping, then she'd fall asleep on me (for about 15 months) and then I would put her in her crib. Now I stay with her after putting her in her crib until she falls asleep.
I don't have a second child, so it is definitely easier to do these things, I know, but what do you think your son needs to help him to sleep best? Does he use any sleep associations (animals, music, white noise)? Is his room dark enough? Is he eating enough before bed to be full for the night? Is it possible that he just misses you and needs you to fall asleep?
I know you said you've tried everything, and I know taking sleep in stages as I have done only makes things harder in the end, but it may help you for now. Also, when switching my daughter from falling asleep on me to falling asleep in her crib, I contacted Isis Maternity's Sleep consultant, who helped me through the transition. It does cost $99, but I found it extremely helpful. They are very supportive and really help you to get on track with your child's sleep. Here is the link if you're interested: http://isisparenting.com/classes/programs/sleep_support
The most important thing is finding the routine that works for him and sticking to it. Good luck and hope you find what works best for your son soon!
Take care :)