been there done that. Some ideas:
As the others have said you can get homework flexibility (tasks and due dates) written into the IEP. This opens up possibilities such as reduced amounts of work, varying methods for instance he dictates and you write or maybe he listens to that book with you reading it to him or from an audiobook. Also with this you can tune into when he could best do the work--ie maybe instead of work getting in piece by piece during the week you turn it on Monday because he copes (just an example) better with it on the weekend because it's not on top of a full day of school.
Timing was everything at my house--no one here comes home and does homework--everyone gets a snack and a break and we find out what homework time is most productive for them. A child with Pervasive Developmental Disorder (PDD) and sensory issues might benefit from a sensory gym set up in the basement so he can burn off energy after school and be more ready to face homework tasks.
Experiment around with different times of day. One of my kids did all of their homework in the morning because they could nail it in a fraction of the time when they were rested and not exhausted from school. With reluctant homeworkers, I'm apt to slide it right at them when they are taking the last bites of dinner because then there isn't a transition to make. Good sensory snacks can help: licorice, bubble gum, soda sipped through a straw, crunchy crackers.
The real bottom line question with homework should be: Is this assignment benefitting the child?