D..
Added per your SWH:
He goes to bed before you and your husband, right? Put him in the middle of the bed and quietly stand outside the door until he falls asleep. If you aren't comfortable with that, you could go out and buy some guards for the side of the bed. That's what I did for my son's bed once he was out of the crib. You slide it under the mattress and then pull the guard part up. That way he won't fall out of the bed. The hard part is that he will want you to get in bed with him. If he won't go down without you, sit on a chair beside him quietly with the light off but turn away from him. Don't talk. Don't hold him or pick him up. If he gets out of your bed and tries to climb on you, put him back without talking to him. This will prepare him for sleeping by himself. Hope this helps.
Original:
I would first start by night weaning him. He does not need to nurse at night anymore. The way to do it is to turn away from him and let him cry about it. Just pretend that you are asleep and do not give in. He will cry and claw at your nightgown. Ignore him and stay steadfast, no matter how angry at you he gets. Because you have created this problem, he won't just stop demanding it if you don't stop allowing it.
Don't let him fall asleep nursing before nap or before getting in the bed anymore. Make sure that you are sitting up nursing him from now on, and not laying in the bed nursing. He must get used to being awake when you put him in the bed with you and not associate the bed with nursing anymore.
After you have accomplished all of this, with him going to sleep awake, and with no more night nursing, then put his crib mattress on the floor beside of you and tell him to sleep there. You will just have to be firm about it. Maybe you can reach down to him and touch him until he gets used to it.
In a few weeks after you have accomplished him being willing to accept this, start moving the mattress away from your bed closer to the door. At some point, talk to him about his big boy room. Get him to help you redecorate. That will help him become invested in sleeping in his room.
After all of this, then you get him to nap in there. Lastly, you get him to sleep in there. When he comes to you in the middle of the night, you get up over and over and lead him back and put him back in his bed. You might have to do it 40 times in a row. It will be awful. But eventually he will understand that you don't mean maybe and he will finally give in.
I would expect that this will take you about 2 months. Don't let it go on longer than that, truly.
Good luck,
Dawn