I say put him back in his crib, if that is an option. I am not an expert, by any means, I only have one child so far that has moved to a toddler bed. I waited until I felt he was old enough to control himself and stay in bed when I told him to, and he was ready to potty train (plus, climbing out of the crib was becoming far too exciting for him to resist climbing out and destroying his room). He was 2 yrs 9 mos when we made the switch. We told him he had to stay in bed until we came in to get him (which was the same as when he was in the crib). It solved the problem of climbing out because there was no longer a challenge of scaling a crib side, so he obeyed and stayed in bed (he tested it a little later down the road).
If all of the sleeping trouble has started only because of the bed switch, I would put him back in the crib. If he is suddenly waking up frequently and crying (when he didn't used to) it sounds like maybe he is not ready. I know plenty of people who keep their kids in the crib until 3 years old. I don't think it should be so hard when they switch and you should be able to keep the same routine of going to bed. If he could get himself to sleep in the crib and sleep all night, get back to that, then put him in the toddler bed a little closer to 3. You could leave the toddler bed in his room in the meantime, if it's not too crowded, that way he would get used to it and may want to play in it. When you think he is ready for the "responsibility" of sleeping in a big boy bed, talk about it in advance, maybe a day or two before. Let him know it's coming and it is very exciting that he gets to sleep in a big boy bed. And then the day of the switch, talk about it a couple of times, talk about his responsibility to stay in bed and sleep, let him know what you expect of him and give it time to sink in. Try to engage him in the conversation and get responses from him (depending on his language ability). That seems to help with our son, at least. It seems to help him if he has time to think about things in advance. I don't know how much time he actually spends "thinking" about it, but it certainly makes a difference with him if he knows about something in advance. And he is a talker so it's not hard to get him to engage in conversation with me, but it seems to help him understand things better when he makes the connection verbally. I get his thoughts on the matter then I have had him say things like, "I stay in my bed," or "I don't cry and fuss." May sound a little silly, but it helps him!
I hope you find a solution! Good luck!