Maybe slip up the night before and make sure he's eating applesauce for Thanksgiving is an option.
I can't imagine being in your shoes and not losing my mind with rage with some new guy doing that to my mother, and talking shit about about my father. You're a stand up guy.
Maybe if she wants to talk about history, remind her that you weren't raised to tolerate that treatment and abuse of women and that she knows it's not right. I would guess she's just afraid of being alone.
"Silence is Golden. Duct Tape is silver"