Tell him he has to sleep because Mommy and Daddy are going to sleep - make yourselves scarce, turn off all the lights, etc. Tell him too that he is a big boy and if he wants to read a book for 5 minutes he can, but then he then has to turn off his light and go to bed. Giving my daughter choices, that were really no choice, empowered her and took some mystery out of the bed thing.
I am also not above rewards/bribes as long as they are not food. He goes to bed properly for a whole week (use a sticker chart), he gets to go buy a toy or a book.
By the way, I would let him have access to drawers that he can wreck without too much consequence - "This is your drawer to play in and these are Mommy's drawers for your clothes" - just make HIM pick them up in the morning!!!
I get the thing about not locking him in - luckily my daughter didn't really try to open doors until she was around 3 I think. But if you do leave the door open, make sure the house is inaccessible/safe. He may sleep through the night now, but you never know when he could start wandering.