I think his balance could be improved with better front leg plant.If you are catching for him, from that perspective, his knee should be in a vertical line over his ankle. Currently his knee is to the 3rd base side of his ankle. He will be using a lot more energy balancing himself that could be put into the pitch. Also, he’s landing to the 3rd base side instead of following through to the 1st base side, which would be natural for a right handed pitcher. Both of these things indicate that he’s using a lot of energy in directions away from the target line.
There are other things, but I’d like to see what he looks like once he gets his balance corrected. Have him do rocker drills and side hops, etc.