Mighty - I cannot believe that you made your XH's frigging lunches last year. Wow. I would have put rat poison in them.
Now, they do have to try and play dad of the year, because deep down they know they are not.
And two mortgages and no home? Oh that sounds like a good idea.
Please Mighty, disengage. As Job has posted - they sacked us as wives. Don't hang around and sweep up after him. He is conflicted. He is selfish and self centred right now. He has done a stupid thing and fathered a child with a young woman who can't keep her knickers on. He even doubted the paternity. How would you have felt if your xh had asked you for a paternity test. I would have been so outraged that I would have changed the locks! (After assaulting him in a painful place) OK the assault is fantasy, but the locks would have been changed.
What a piece of work they both are. Be glad you are not legally tied to him.
Fwiw I think your xh will work through this, but you need to step right away and let him and his gf get on with it, while you smile sweetly and enjoy the show. It is all smoke and mirrors, not the real thing.
Drop the rope as much as you can. You are one strong woman.