Sorry, I was away for the weekend, only just now got home.
This is just a shot in the dark, but can you give him some pain meds about 20 minutes before you put him down? If he's cutting teeth or has an ear infection or is in some other discomfort/pain so he can't settle properly, that might help break the cycle. It might not tell you the cause of the pain, but it might help you find out if pain is the issue.
Has reflux been ruled out?
As for bedtime, I hope you're able to get some respite by handing baby off?
Will ponder some more....