What I read in your other threads it was quite a bit more than just snapping at him. I am not judging you but I don't think that is a helpful way to characterise it.
Anyway, I can see you are really wanting to change what's been happening and help him. It's terribly hard when you have a baby and other small children to look after too.
Have you considered a course of psychotherapy for children which is very play-based? I am a huge proponent of psychotherapy and have also seen just how powerful play therapy can be with children. I am not talking about a lifetime of therapy for your son, but just to help him when he needs it now.
FWIW my son has had very intense periods of anxiety. He was by temperament an anxious, timid child but the huge ramping up of it was caused by seeing/ being a part of some frightening/ out of control situations in our family (we have a child who has quite profound SN and we have been in some very bad situations). He also used to run out of the room at programmes/ films with the slightest element of dread to them. But for a while he really was in a bad way tbh. It did last for quite a few months but slowly decreased. He is, touch wood, two years later completely different. Completely.
I did a hell of a lot of 'work' with him about his feelings for a long, long time. Lots and lots of acknowledgement that there had been scary situations for him. Going over the scary scenarios and his feelings. Accepting that he was angry with me too about some of it.
I slept in his room with him. We read Willy and the Wobbly House by psychotherapist Margot Sutherland. And lots of other things, with a broadly psychotherapeutic approach inc him joining a support group. It worked for us but did require a lot of work, over a long timescale. It's been so worth it though!