*He's got dysgraphia but I really don't think that's at play here. I don't think.
NikiHarp,
I unfortunately don't have time to give a thoughtful response at the moment with actual advice, but fwiw, what you wrote sounds so much like my dysgraphic ds at your ds' age. And like you, I thought it was perfectionism at first. Hindsight proved it to be issues related to dysgraphia.
My quick advice for right now is to think through - how would you approach this if it is dysgraphia and try it from that perspective.
I'll try to stop back later with some actual advice!
Best wishes,
polarbear