This has been really interesting to read.
(Sorry OP that this might feel it's a bit off tangent from your original post, but it's hopefully useful insights into PDA).
For me, it's not just the demand avoidance part (which DS has in spades), it's the other bits also often cited in the presentation such as a fixation on other children. DS does this - both positive (possessive) and negative fixations and it's incredibly challenging to manage - this as much as the demand avoidance itself.
Maybe this is often present in autistic children, but I do hear it often linked with PDA.
There's no easy solution I don't think - DS has been part time at school for nearly 6 months now and we're on our 3rd autism specialist in 2 years (all have been very good but massively overstretched. And we have no EHCP, unless we win at Tribunal, but that's another story).
He can't cope with the noise of the classroom plus his unpredictability around the other children is v challenging.
He's really bright but refuses to take on any new learning (but before learning became a requirement he gobbled if up - I remember asking for workbooks for his birthday pre starting school as he didn't play with toys and loved completing them. Now he's refused to write since October last year).
He does cope better with routines though, but finds visual timetables etc too overwhelming - even now / next is too much as he likes to choose himself.
I hoped by reducing his anxiety at school (which everyone involved has worked really hard to do with some success), his demand avoidance might decrease too; but this has not been the case (although rather than exploding at school he now at least uses charm or procrastination!).
I can't tell you how I much I hope his demand avoidance doesn't turn out to be pervasive and long lasting but so far no one's been able to break through. I live in hope we can find a way to harness his wonderful brain without doing his mental health any harm.