I can't speak from a homeschooling perspective, but can only offer some thoughts as to what is keeping us surviving - or not - with our own writing issues.
First thought: I have often seen homeschooling parents on this forum recommend a "detox" period, especially when you've had an abrupt start following a bad school experience. So to your question, "Can I let go of the writing for one season", it may be worth considering if there's really a good reason why you can't. Is there one particular activity that is causing him the most stress, and can you live without that for a month or a term?
Within the school context, we've spent a couple of years trying to figure out what output might look like in non-written form. Our DS doesn't seem dysgraphic, so taking out the handwriting aspect doesn't help him much. For yours, however, that might be a significant and helpful change. As polarbear suggests, there's lots of alternatives to handwriting and spelling, including typing, word recognition and voice recognition software. If any of these help make writing feasible for your DS, they are NOT cheating!
Another option is to look for alternatives to traditional written output. Posters and flowcharts, for example can be good for the visual, non-writing types. Diagrams, drawings, storyboards and comic strips. Build it in lego, popsicle sticks or Minecraft. My DS loves PowerPoint. He's now learning the "Inspiration" software, and using it to brainstorm, capture data, and structure and build presentations. Some day, we'll move to trying to use it to help build text outlines, but, well, maybe not yet today
Are there types of writing that work better for your DS than others? My non-writing DS is inexplicably happy writing poetry that follows strictly-defined patterns, like haiku and pyramids. I haven't yet convinced a teacher to try letting him response in verse to a writing assignment, but I'm working on it. My dyslexic DD, on the other hand, loves to sing, and will improv lyrics on the spot all day long. Again, I'm still trying to convince a teacher to try asking for her response in song rather than on paper...
All that to say, there are so many ways a kid can demonstrate their understanding, analysis and ideas. Perhaps a few months of creative thinking and exploring output in non-(hand)written forms might be just the ticket to ease your transition.
Congrats for taking the plunge - all the best to you. Hope it goes well!
