T.H.
Well it sound like you're doing it all "right". Are you waking him up during the day for his every 3 hour feedings? If not, do it. I fed my kids at pretty much exactly 3 hours and I woke them if they were asleep. It really worked like a charm. Eating around 5-6 is fairly normal, but both mine didn't go to bed until about 8...so, not sure how to make that happen b/c I agree you don't want to make them over tired. Actually I would probably feed him at like 5-6, let him sleep if he wants and then wake him up to eat again around 8-9 and then put him to bed for the night. He'll probably stay asleep right? That's what I'd do, maybe it will help! Good luck!