HaWho, I don't want to chime in with D advice since it is not in my realm of action but I wanted to say that I get the sense you are allowing yourself to be dragged into the darkness a little on this. Isn't the Costco card just a membership card that allows you a discount but isn't a credit card, for example? Why give that any of your head/heart space? He just seems so sad and pathetic to me, like an angry bee who doesn't realize that after you sting, you die. He is enslaved by his anger and depression, but you don't have to take that in. For things that don't matter, can you just ignore it or say, "we can share the discount card," and nothing else if he asks for a pathetic connection like that? To me, when I read your sitch through my faith lens, your H seems caught so deeply in a spiritual battle, he is still so confused and to my mind does not want to D but is being driven to it by the dark MLC self he can't master. I'm not telling you to stay or to go but only saying that I would only battle things that actually connect you financially and the rest just lay at the feet of the universe and don't take it in. Of course it's not going to be fair, the whole thing is disgusting, wrong, a betrayal, etc. And of course you have to make sure your kids are supported financially. But wherever you can set a limit to how much tug of war you are going to play, the more free you can be.
I believe I will see the bounty of the Lord in the land of the living. Wait for the Lord with courage. Be stouthearted, and wait for the Lord.