Back to your S, because you're right, he's the one who has very little say in how his life goes. (I'm not negating your stress but you'll work through it and you have an IC)
S isn't too young to have someone help him sort out his feelings. Your city has lots of resources, research play therapy. If he's that distraught every time he has to go to XW, he needs help navigating that and you need help helping him.
Me 57/H 58 M36 S 2.5yrs R 12/13
Let me give up the need to know why things happen as they do. I will never know and constant wondering is constant suffering. Caroline Myss