I'm not going to help my ex with university stuff I promised I'd help with
Why wouldn't you help him?
Maybe he wants me to keep a promise, but I don't want to
You don't have to do things for an ex. But if you promised to help already you shouldn't back out of commitments.
He didn't give a shit about me so I don't need to fulfill what I promised either.
Well that's fine, I think in this situation you can refuse to help an ex if you are no longer together.