a 36x12 is recommended for an ADULT ball python. A baby can get lost in so much space.
I say try it out for a week or two and if the snake is having feeding problems, downsize to a small 6qt tub. I have a feeling you won't have too much of a problem with the large enclosure though. Just make sure there is enough hides, lots of cover, and the back and sides are covered with dark paper. The main issue with big tanks is that they make it difficult to keep proper temps and humidity levels. Generally you will be stuck with a humidity draining lamp just to maintain adequate ambient temperatures.
Just a note though, your snake should have two identical hides. One for the warm side and one for the cool side.
Also, climbing the walls is him trying to find a way to escape which can also sometimes be a sign of stress.