My WS has always said, as well, that he doesn't want to be a father to anyone else's children. His AP has two, but she divorced her husband and moved into an apartment, leaving the children with her ex. (One more very fine feather in her cap, I might add.) In theory, there's no reason why he couldn't have moved in with her as soon as I kicked him out. And yet he hasn't. Despite her invitation to do so.
The why is a huge question for me. Is it that he's uncomfortable having the kids come over to a house he shares with her? Maybe. Our kids know who she is and so would obviously have questions about how that relationship came about. He could, however, just see them here as he does now and they wouldn't be any the wiser. In theory.
I choose to believe him when he says that he hasn't moved in with her because he doesn't want to. Even though there's really no reason to believe anything he says about her. But I do. I believe (and this is what he tells me) that he won't come home because he doesn't want to make a decision about his future with me. Perhaps I'm a fool for believing that but I would rather be a fool (again) than to assume the worst. To me, it says a lot that he is staying where he is (on his own) and not living with her. He's headstrong and stubborn and if he really wanted to be with her I think he would be. Caution be damned, he would do it.
I just wonder whether your husband did mean it when he said he would never choose her over you. Are you really sure that his struggle is about her over you, or is it possible that he, like I believe about my husband, is simply struggling with himself and you. If they don't know whether they can make it work with us (regardless of how we feel about the validity of that question) I think I understand why they won't let go of the OW. Perhaps the OW is the consolation prize?? Just a thought, one that I'm wrestling with as well. I don't know the answer.
This is an interesting way to think about things. I know my husband has really struggled with me and him.