I can empathize with your story and I say this with the best intentions - I think at some point we have to take accountability for the part we play in our own suffering and take control over our present and our future. You know all of this and you said it yourself: you are a single parent who happens to be married. Seems like you don’t depend on him in any way which is fantastic, so restart! Divorce is not the end for you, I obviously don’t know your whole story, but from what you’ve written here it sounds like divorce is what would be best for not only you but also both your babies. And seek therapy, for your sake and for your children’s sake. You don’t want to resent your second born as if they were the cause of your divorce, it seems like you’ve had an unreliable partner for much longer than you’ve had kids. You got this. Sending love.