Well, he's now shown you exactly who he is. An unremorseful asshole who intends to stay up to his balls in OW. I'm so sorry. He is playing you. Big time.
Let me tell you a secret. The worse thing in your life right now is not a divorce. The worse thing is to be the fall-back position, Plan B, the alternate, in your marriage. This is the position that he is putting you in. Right now, he has it all. You are at home for him taking care of the house and the children, existing on scraps that he negligently throws you, while he is living his Life O Lurve with his whore, excuse me, FauxWifey. Why should he change? He has it all. And he's going to keep on having it all, at you and your children's expense, until you change the rules.
You really, really need to see a lawyer ASAP. I personally would out him to my family and everyone else he's introduced the OW to. I would also contact OWs BH and tell him exactly what it going on. Nothing, nothing will change until you re-wright the rules. It's time to concentrate on doing whatever it takes to keep you and your children protected from his horrible decision to be an adulterer. OK2014, realize that he has introduced YOUR CHILD to his Ho to prep him to "gain" a new mommy. His intent is to replace you. He is NOT thinking about you at all, except as an inconvenience that he knows will soon be out of his life. You need to stand your ground and start fighting. It's hard. We all know it is. But you don't have to play by his rules. Start shaking his fantasy world up right now. Or you will be living this nightmare for a very long time and it will only get worse from this point on. (((hugs)))