DS3 was a horrible sleeper. We ended up putting dark sheets up over his windows to block out the light. We were moving soon otherwise I would have put up room darkening shades. If there was any light coming under the door he'd yell for me too.
If I were you I'd try (not necessarily in this order) tanking up on a favorite heavy meal to make sure he is full before he goes to bed, a white noise machine, room darkening blinds, the sleep fairy cd that many parents have had luck with here, making sure he gets a good workout in during the day to wear him out, putting his crib back in his room, asking the doc about melatonin for him, making sure there is nothing in his room to irritate his allergies, giving him Advil before he sleeps in case he's in pain, OR cosleeping. But if you cosleep and have other kids who want to have access to you at night but you don't want your baby escaping while you are sleeping, I'd put a gate across your bedroom door.
I hope ole you can find a solution that helps! Sleep deprivation is awful.
" I object to violence because when it appears to do good, the good is only temporary; the evil it does is permanent." Mahatma Gandhi
"This is the ultimate weakness of violence: It multiplies evil and violence in the universe. It doesn't solve any problems." Martin Luther King, Jr.