C.
Hi K.,
My middle child was quite the escape artisit when he was little, so I know what you're going through. Try putting a gate up in his doorway. If he can climb over the gate, which mine could, then put 2 gates up. I know it sounds crazy, but I had to do this for my peace of mind. I was afraid he would wander around the house while I was asleep and possibly get hurt or even get outside.
Hope this helps,
C.