K.S.
By what you are saying he does got the bathroom down with wetting in the potty. Try this put a pull up on for bed time and put a small port a potty child size in his bedroom or out by his door in the hallway for a while and tell him if he has to go he can put it in HIS potty and see if this works. My to sons did this because they where comfortable in their bedroom at night time and they did not want to roam around in the dark to go to the big potty. I know this is a pain and sounds gross to be pooping in your bedroom but as soon as he does that you should be able to move him to the bathroom with a night light during the night.
Good Luck,
Kim in Ridley