A good mother will prioritize the wellbeing of her children over winning a conflict with her (ex) partner. It is completely unfair of her to ask you to pick a side or go no contact with your father. Hopefully she’ll realize this once she’s had some time to process her (understandable) emotions. In the mean time, best of luck to you!

NGL, IMO your dad sounds like kind of a piece of shit (based on the limited information available to me). However, at the end of the day he is still your father and it’s not your job to punish him for that. That’s your mother’s lawyer’s job.

Be there for your mother if you feel up to it (and you love her), but keep in mind that it’s a parent’s job to emotionally support their children, not the other way around.