I am so sorry you are scared, and I dont blame you. My son is struggling in a different way, but they are still our babies.
You have to be strong for your son. He has to see that you are there for him, that you care, that you will help him in any way that you can. Be consistent and loving, with definite boundaries and take it from there.
Forget about your h right now. He is in lalaland. You do what you need to for your son. Your h is unable to right now. He is in his own crisis.
Try not to get bogged down in your anger with your h. You are giving him too much head space. Worry about you and your son. That's it. Dont worry about h or fixing your marriage right now.
Come on, S. Regroup and concentrate on the task at hand. Stay stong. You and your son are in my prayers.