Hi OP, hopefully you’ve all managed some sleep. Unfortunately, MH help is so hard to get. Getting information yourself is so important. I agree with others A&E is abysmal with MH, It almost invariably makes things worse.
Here’s a link to a summary of some immediate MH first aid techniques https://www.calm.com/blog/vagus-nerve-reset-for-anxiety
I would also recommend Looking up the Polyvagel theory by Dr Stephen Porges (Debs Dana makes it more practical)
The body keeps the score by Professor VanDel Kolk, although primarily about PTSd maps well onto anxiety.
Everything your son’s mind and body is doing is doing it to try and protect him. It just doesn’t realise there’s no actual danger. It sounds like he’s been through a lot recently so it’s not surprising his mind and body are struggling.
It sounds like you’re doing a fantastic job. It sounds like your DS is a bright lad and knows what help him, so yes if movement/football helps, play into that. Go to the park, kick a ball round.
I often go into freeze then if I’m feeling safe will move into flight so will literally run. If it’s safe allow your son to run somewhere (although be careful as it’s likely things like road safety will be non existent, so round the garden is good).
Hypnotherapy can work well at your sons age.
if he is predisposed to anxiety getting a good grounding in coping mechanisms will help him throughout life. We are all different, we’ve evolved to react differently to the world. Everything will be fine. Your son has a loving supportive family to help him navigate this. It’s difficult to se loved ones going through this, so big hugs to you, and as I said upthread make sure you look after yourself too