You can mist him daily, or put an air stone in the water that'll help keep the humidity high. As far as lighting goes, they're nocturnal so you just need to keep somewhat of a consistent day/night cycle and don't turn the light on at night in the room where they're at. If you wanna view them while they're active, get a red or black light bulb.

If you want him to stop walking on the sides so much, put a stick diagonally in the corner, slanting down from near the top, and he might end up spending more of his time on the stick.