The sooner you stop asking "Why is he doing this to me?" and simply focus on getting done what needs to be done, the sooner you will be, well, DONE. There's no excuse or justification for what he's doing, so stop looking for one. If you go forward not expecting anything from him other than resistance every step of the way, it will be less painful and over with a lot faster.
His whole strategy is to make you pay, emotionally. Don't let him win.