Sorry, this is a little long...
My 2 yo (32 months) DS co-slept exclusively, until he was 25 months old and just about weaned. We then moved him in with his brother, who is exactly 2 years older. He sleeps on the bottom bunk, which is on the floor. He was pretty ok with this move. He gets in bed with me in the morning, and we still rest in the afternoon together, although he just dropped his nap.
In the past 2-3 months, he has had a really hard time with staying in his bed. He goes to sleep just fine, independently, happily. Somewhere in the middle of the night, he would come in crying. DH (does all the nightime parenting!) would bring him back to bed. Then DS stopped coming in crying, and just crept in quietly, and get in bed with us. I would wake up with him there, having no memory of it happening! Now, over the past month or so, he has been waking up hysterical, sobbing and screaming. He doesn't calm down until he is in my arms. He is gasping for air, shaking. Last night, he said he didn't like the dark, which he has never said before. Their room is dim, but not even close to dark. He has his special blanket, special stuffed animals etc with him.
The thing is, we cannot co-sleep. I work from 8pm-2am at night, and in general, get 4-5 hours a night. With DS dropping nap, I am struggling. DS is a restless sleeper, tossing, turning, talking in his sleep. If DH works on getting him back to bed, I am awake the whole time. Most nights, I am getting 4-5 hours of very interrupted sleep. I can't function on that or drive back and forth to work safely.
What can we do? How can I help him with what seem to be nightmares? How can we gently work towards him sleeping through in his own bed? He is very articulate and also, very stubborn. For example, we have tried stickers, special surprises in the morning etc, but he isn't motivated for them. He likes getting them, but doesn't care in the moment.