difficult child 1 has huge abandonment issues. It takes a lot for him to "let people in" and he's had so many "leave" that it throws his whole world upside down when they do. In our case, the people just vanish, as in never see or hear from them again and have no idea where they even are. difficult child 1 went through a long period where I had to tell him constantly that I wasn't going anywhere and he'd test and push to prove to himself that I really wasn't. Your son heard what he did and that just hoovers. Your H is a jerk with bigger issues than your son has. Your son needs to be told and told repeatedly and often that YOU don't feel the same way and that since your H is making you "choose" between him and your son, that you are CHOOSING your son. He's going to need a LOT of reassurances, no matter how bad the behavior might get (it's all just him testing your words) and how many times he "tries" to push you away, if he does.
You're doing a great job and I am sending strong shoulders and supportive ((((HUGS)))) your way.