Hi sciencelover. We just got back from assessment with the educational specialist for my DDs visual spatial learning. We will get the report in a few days. The specialist talked to DD a lot about visual spatial learning. One thing she recommended was learning to touch type to help overcome both the physical difficulties of writing, but also the mental challenges of getting started with writing. The following site is free and is for kids.

http://www.bbc.co.uk/schools/typing/

She told DD that when she can't think what to write to just download her thoughts by typing. I have seen a suggestion where kids type with the screen off or covered so they can't see what they are typing. It lets them write freely without getting caught up in typing errors or self editing. Thought that might be something to try with your DS.

The specialist also talked about the value of mind mapping. There is an app for mind maps. Look at www.inspiration.com

For exercise, DD has a fit ball for physio. There are a lot of exercises you can do with it that strengthen the core muscles and can be surprisingly tiring while kids stil feel they are having fun.
If we get any other tips that might be worth a try I will pass them on.
Hope you are finding a way forward.