That’s an unreasonable demand on his part. There’s no guarantee that one party in this business is a saint, no matter how scummy the behavior of the other party. Real life does not work like that.
Any unreasonable demands he makes on a third party, of course, have nothing to do with whether she deserves to get alimony or not. But her awful behavior doesn’t make everything he does right.
This. She may never see you as an adult, and might act ‘betrayed’ if you point out her wrongdoing, but if you can get her to see she CANT WIN, then hopefully she’s smart enough to let it go and GET ON with her life. Sounds like she has one, and she’s wasting it. Do her a favor, and smack her upside the head <figuratively> Surely she’d have done that for you when you were being stupid?
Lots of parents see their relationship as one-sided. Just because mom chastised OP as a kid when he was being stupid doesn’t mean she’d welcome the criticism directed at her, now.