10 pm isn't early...it's late. I think 8:00 is a good time to shoot for. And if he goes to bed at 10, what time is he getting up? Try waking him up at 6 or 7, until he gets on a better schedule.
...also, look at how many naps he's taking. Probably should have switched to one nap around this time...mine recently did, also 15 months old.
All that said, my 15 month old wakes up several times every night to be nursed, and I don't know what to do to stop it!!!!!!! :) And I have a really hard time getting her back into her own bed after I take her out of it. She ends up sleeping with us, too.