Gosh you poor woman.
Just know, its shit right now but it is temporary, won't be like this forever.
Tonight do your bedtime routine, bath, book, 'night night, I love you', bed. Keep it snappy, after his bath try to have him down within about 15 minutes so you're not dragging it out.
Try to make sure he's had enough to eat to avoid hunger waking.
Go into him if/when he wakes and keep taking him back to bed. If he gets to the point where he's hurting himself again you'll have to stay with him in the room. If he's banging his head just keep moving him away from the door.
By you going into his room rather than you bringing him to your bed you're reinforcing the idea of him sleeping in his bed in his room. You may have to hunker down for the night lay on your duvet with a pillow and blanket?
It's absolutely awful, I know. But he has to sleep!
Is there anything else going on with him? How is his communication? Is there any additional needs?