It's all about control. It might be good if he did see your son's therapist. The therapist may then have a better idea how to work w/your son. It is important that he get the medical assistance he requires in order to work through his depression and anxiety. Who cares if your h throws a hissy fit? You are the primary care giver and his mother, as well as being the sane adult right now.
Yes, the monster comes out to play quite often when they don't get their way. I would venture to say that something has rattled is cage a good bit yesterday. Don't engage w/your h again for a while. He wants fuel for the fire that is raging within him.
Yes, you do have a long road ahead of you, but if you stick to your boundaries and not back down, you'll be okay.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.