Hmmm…
Maybe this will sound crazy but how about befriending the husband? Not you…but perhaps your dad. I get that you guys don’t like him…but…fake it. Not hang out with him once…but several times. Maybe he’ll feel guilty/motivated when he’s surrounded by guys who are men…who might encourage him to treat his wife better. I’m not saying that he should be lectured on how to be a better husband. A lecture would backfire big time, I think. But maybe…in sneaky little ways…with the right choice of words…they can get him to act like more of a man. And maybe they can show him how a wife should be treated.
He seems like a guy who is whipped by his mom and sisters. Maybe he doesn’t have many positive friends to learn from. And his only…cough…“role model” is mummy the monster. He may not be crazy about the guy’s in your family such as your dad…but maybe you don’t have to use your dad in this experiment. You could ask other guys.…those that you trust and will play along (do some acting…get a drama with a good cause going)…to help you out. What do you think? Is the plan too crazy and out there?