What state are you in? That sounds like serious BS to me.
You do what you are comfortable with. You want to fight this then fight it. Don’t agree to anything that gets you closer to D.
And be careful. My gut says there’s an OW. Probably not serious, probably more serious in his own head, but really, that’s all it takes.
What are you doing to GAL? What days do you want him to take S? One thing that worked for me….when H left, I didn’t give him a specific schedule with S. Then after this went on for a bit, I did. He has H two nights a week and every other weekend. H can’t take S overnight because he has to be at work very early and S is too young. So H stays at our place on his two nights and he stays at our place on his weekends too…not because I told him to, because that’s what we worked out. I refused to raise S alone. I told H “You can walk away from me, but not S.” I was fortunate. He agreed pretty easily because H is a great father. At first I told him on your nights you can take him to your place or you can stay here in the guest room. I think it would be more settling for S to be here, but I leave that completely up to you. Take some time to think about what’s best for you and your schedule and what days you want. H agreed to be at our place on his nights with S. And the other great thing about it was DB Coach and therapist both encouraged me to spend more time with H since I had some pretty big changes to make in me and I needed him to see them. Also, in hindsight, I needed to see them to and no one can push my buttons like H, the good ones and the bad ones! At first H would take S out to play and then put him to bed and leave around 9 or 9:30. I think that got old and things with he and OW took a horrible turn so one day I noticed he had an overnight bag. I said nothing. He stayed in the guest room that night and that’s when he started staying over. This was in early February, right before Valentine’s Day. Then before March he was back in bed with me.
Not sure if that would work for you, but it did for me. Take it with a grain of salt.