You strike me as a warmhearted human being, who may be somewhat impulsive and acts from her emotions in the moment. The same characteristics that can make you a wonderful mother can be a disadvantage when dealing with a partner who cares more about his own interests than your’s and the children‘s.

Of course it is in hs best interest to come back and change as little as possible, just enough temporarily for you to cave and let him back in. He knows you are weak-hearted when he throws the love or family card.

I don‘t know if you know the Harlow experiment with monkeys klinging to a fake fur or even wire mother, because that is all they had. You can google it. I myself have known a time where I was klinging to the wire mother, hoping to turn it into a real person, by being nice and loving enough.

But that is not how a loving relationship should work. You should feel cared for. You should feel as though he would put his life on the line for you as you do for him. From what you told us it is clear that you are doing your best to make things work, while he is doing only what suits him and is basically stringing you along, probably until you are fourtyish and he will exchange you for a younger model.

Of course you want the family together and you want the times back when he is nice and you have great times. If only he did not have this other side. If only he had a real heart.
Do you think he would take you back if you behaved to him as he did to you in the past? Think again.

It is normal that you have loving feelings for this person that you have been attached to. It means you are a loving human.
But if he is not willing to change you will be clammering to the cold wire mother, rocking yourself to sleep and pretending to be in a loving relationship.