Homework at this age should be no more than 20 minutes a day and legally is not compulsory.
In the case of your son OP, it should also be differentiated. My son has ASD and we have similar struggles. It's not that he doesn't want to do his homework, it's that he wants it to be perfect and struggles to retain the pertinent information.
Sometimes I stop him after doing the first 'challenge' as they're called. Other times if he is handling it well we will do all the challenges under the agreement that practice makes perfect. He only gets one piece per week, it is assumed they will read at his age (yr5) and spellings and times tables are to be practiced regularly but they don't set it as homework.
I have always praised effort over achievement, which works for DS and he now knows as long as he is trying his hardest he will be praised for it.
I still have to sit with him for big tasks. Smaller pieces I will leave him to it, check for errors and ask him to try again, like they do in class. I helps him to have this routine. I had to do this as he got lazy, learning that if he played dumb the TA and me would do his work for him.
I think for you average child a 6 week project at this age isn't demanding, but for your DS there should be some leeway. But at the same time, school just let missing or incomplete homework slide with my DS, as long as I added a note saying we'd stopped after x amount of time or because of distress. Because there were never repercussions DS is more willing to complete his homework now.
I could leave DS alone completely with a making task - he is very creative. In the holidays they asked them to do 'a project' on their theme topic but it could take any format they liked. DS took the opportunity to combine his love of the topic and making videos and now has a fab video on YouTube. I held the camera, but everything else was his doing. There were no prizes, but he got a headteachers certificate for it. Sometimes you have to just roll with the punches and work with their strengths.