My DS2 was a bit older about 16 months, but went from sleeping through to waking every night or second night at the same time 11pm and screaming. Like you I tried everything and it was after 2 hours he would normally pass out and sleep peacefully. In the end I took him out of his room (as he shares with DS2) and would sit in the dark lounge room giving him cuddles while he would lay there awake just staring. Finally his eyes would shut and I could put him in his cot.

This lasted for 8 horrid weeks and then suddenly he went back to normal sleeping through once again!