You sound like you have given lots of things a try, he sounds a bit like my son at 4mths. It does feel like they need to cry before the go to sleep. My son used to like to cuddle something that smelt of me. I used to give him my night shirt to cuddle then take it away once he was asleep because I used to worry about leaving it in his cot. Sorry I don't have a magic answer for you, best wishes.

PS. That is a gorgeous pic. of him.