It must be very hard on all of you, especially your son - I do really sympathise. Traditional teaching does indeed have its weaknesses, and I've heard many parents say similar things. I suppose the trouble is that it's aimed "at the masses" (well, about 30!) which doesn't always suit individual needs. I'm sorry to hear you had no guidance from the EdPsych, but it's great that you already know how he needs to be supported. Hopefully the tertiary services will be able to also give more guidance on fitting that in with the way school works.
I've just re-read that link I suggested earlier (www.pdacontact.org.uk/noframes/guidelines.shtml#Handling) which was the site suggested by the Autism Society. It seems to be saying that the key isn't so much differentiation of work as different handling of the child by a trusted key worker. If the school haven't seen it, I'd print it off and give it to them, since it offers some useful tips on how they can get the best from a child with PDA. (Which they will need, since the site is saying the opposite of how you'd usually handle behavioural issues.) The same site also offers training to schools - maybe suggest that to them? Since it sounds like the key difficulty is that they aren't sure what to do (despite being happy to help). I know if I was teaching a child and lacked the experience of his particular need, I'd want to know as much as possible.
With that in mind, I'd suggest that you personally are also a very useful resource to the school. If you tell them ways in which he can be supported, perhaps they can respond with suggestions and you can then explain whether that would work or not? If you put your knowledge of your son and PDA together with their knowledge of school/curriculum, they should be able to come up with something.
In the meantime, I'd guess (and it is a guess as I lack experience here) that they could help him by putting more choice into his tasks, because one of the key things about school is it tends to be highly directed activities, which as you say won't suit his learning style. So, for example - give him three worksheets and let him pick which one he likes. Put work in different places around the room and let him choose where he wants to work. Offer challenges and puzzles to inspire him ("Can you help me here? This work on materials does seem a bit boring doesn't it - can you find some more interesting facts about it?" He could then make those into a mini book). Set more open-ended tasks, such as "can you show me what you know about xxx?" Give him projects to work on which capture that thirst for knowledge. Offer him various ways to present his work, for example it could be a picture, or writing, or he could make a collage. Let him choose which books he would like to read. This way they can hopefully include him in both content and learning of skills, but allow him some control.
I really hope that's of some help - I saw the PDA contact site also has a parent forum, so perhaps you could ask other parents what their schools have done to help? And I wish you and your family the very very best of luck!