Hi. My daughter has PDA. She was diagnosed aged 7 and is now 25 so I have a lot of experience!
First thing I wanted to say is that you can have the demand avoidance without full blown PDA, which is the autism diagnosis.
No one ever believed by daughter was on the autistic spectrum - teachers would tell me they didn't see it, even as I was pointing to the CAMHS official diagnosis report!
The thing about PDA is that it is known as the social autism. It is often the autism where you keep looking at the list of autistic traits and thinking it can't be that because of the eye contact, sociability etc.
In fact, my daughter was way too sociable. It was utterly over the top and often inappropriate- she would chat to a teacher like she was her friend, she was incredibly bossy. She was in fact role playing, which is a common PDA trait - none of it was authentic but it fooled lots of adults into thinking she was advanced socially.
She wasn't academically able but of course some kids with asd are. Some appear to be really able but it is actually just some form of precocious reading and it falls off as the child ages and has to do more creative work.
Anyway, my advice to you is:
Get your son assessed by expert Speech and Language Therapist and Ed psych. Use people who are familiar with PDA. You also need them to be used to tribunals as you may need their reports for an ehc plan. Don't think you don't need Speech and Language - for a child with a PDA type profile it is possibly the most important of all. It is not about how they pronounce words but how they talk and interact.
Read "The Explosive Child" and make your parenting low demand. This doesn't mean they get to do what they want but don't get into unnecessary battles.
Always priorise your son's regulation of his mood - when you first start to see it go, be ready, better still manage his life so he doesn't get there In the first place. Regard his outbursts as panic attacks and you will find it easier to manage them.
Get hold of a book on sensory processing and do activities at home. Find out what calms him - my daughter sucked a dummy til she was 11 (at home) and it was what worked for her when she got in from school.
Don't fret about what other people think or tell you. My daughter never did a single chore here - not worth it. But she lives with her boyfriend and is managing fine because she isn't being asked to do sth.
Accommodate his needs where you can. My daughter hated surprises so we would let her know what presents she was getting. She hated characters in costume so we didn't force her to have her picture taken with Mickey Mouse at Disney.
Our daughter did go to school - I never had to home educate - but she was diagnosed early and we got her assessed for an ehc (over her school's wishes I should add). I suggest you contact SOS!SEN for advice re school.
Once you have your private Ed psych, speech and language and OT reports, you can use them to get more support. Gp for a referral for asd or adhd assessment. You could possibly apply for DLA.
Good luck.