Oh that poor man. He's been horribly mistreated by his adopted mother - treated like second best. And now he's found someone who, in the midst of a marriage that was perhaps more troubled or less fulfilling for him than you realised, he's found someone who feels like is going to put him first. It's so unhealthy but I can understand why he's doing what he's doing.
It doesn't mean you have to tolerate poor behaviour. It doesn't really change anything at all about what you need to do. But perhaps finding a bit of pity for him will help calm things for you. This is a huge emotional crisis for him and he's probably only talking about divorce because he's panicking. Do whatever you need to do to keep things calm. Be out of the house most of the time if you need to, seeking your own support and solace.
I think you can be sure this isn't about you, even as there's stuff about yourself to work on. You can't make him speak to his rabbi, but perhaps you can seek some counsel and support for yourself? Does he have brothers or men friends to look out for him?
