Welcome to WP! I hope you find it at least a little useful to visit here.
I'm Autism Spectrum Disorder, Level 1 (Mild), and I'm 67, so I'm not exactly like your son. Well, if you've been browsing around on the Internet you have likely already read the observation: If you've met one Autistic you've met one Autistic. That is, we are all different.
Things I remember from my distant past childhood:
*-- I was the oldest child. My younger siblings did not hang around the house much so I got to spend a lot of time alone. I liked that.
*-- Before I was ten, I think, I had my own bedroom. I liked that!
*-- When my parents "decorated" my bedroom they consulted my tastes. They showed me color samples to choose from. I chose -"cadet blue" for the walls-, -a darkish blue for the carpet-, -black for the bedspread, curtains, and painted furniture (and for my towel and washcloth). They thought it was boring and dull but they did it!! Plus, they made the curtains not-just-black-but-light-blocking! Some of the furniture had white in lesser features but it was OK. I was very comfortable in that room. (And, it turned out that when my Dad had to work night shifts he discovered my room was a great place to sleep during the daytime.)
*-- I was apparently inattentive in second grade and grabbed a book at home that was way too advanced for me...my parents had a parent-teacher conference and came home with Tom Swift, Jr., And His Giant Robot! I will be eternally grateful to that teacher! My parents kept me supplied with books. Books that I liked. In my case, that meant a lot of science fiction and frequent trips to the library. I liked that! And, I think they liked it that their grade-schooler wanted to read "real" books (Tom Swift, Jr., Hardy Boys, H.G. Wells, Jules Verne, Sherlock Holmes, etc.).
*-- We lived in the outer suburbs and there were a lot of woods and undeveloped land that I could spend time in. And a small number of boys my age to spend time with. That worked well. (Except the bullies were horrible.)
Your son's tastes, interests, and preferences might be completely different than mine, of course. But...I was 64 when I found out I was Autistic. My Dad is still alive so, predictably, I queried him a bit about when I was very young. I really like one thing he said:
<=+=>We saw that you were doing weird things
<=+=>but we decided you weren't being bad, you were just like that,
<=+=>so we decided not to punish you.
<=+=+=+=>I am so glad!
I worked out OK and have done reasonably well in life.
P.S. I still use black towels, washcloths, and hand towels.
_________________
When diagnosed I bought champagne!
I finally knew why people were strange.