@margrethe All I can say is if I was in this situation- I would stay and try to make it work. The next few years will be just exhausting and mentally draining!!!
I’ve contemplated leaving my husband a bucket load of times- lol. When the kids are that small, there is no relief.
It seems like he is willing to help, but just an idiot-
I would demand he pay for help, a nanny or cleaner or something 1-2 times per week (maybe he can issue that trust fund money).
I think the concern that he would just remarry and use that money on his new family is probably what would happen. However, I am sure he isn’t even thinking divorce is where your headspace is at. I definitely wouldn’t jump off the ledge. Also, in the divorce he would get AT LEAST 50% custody, can you imagine not seeing your 3 month old baby for an entire week!!!! New mothers have tried to get the courts to agree with the temporary full custody while the baby is a newborn, but Courts still grant custody to dads- so you just pump and hand over your baby/ milk. It would break my heart.
Can you vent to his sister or mom to talk to him?
I think maybe virtual couples counseling is another obvious option, but when my kids were that age I didn’t have the mental capacity to go there.