Is it possible that he has ADD-inattentive not autism? Not everyone is hyperactive. I never got a real diagnosis for my younger son, but most of his school issues seemed to stem from disorganization, not being an aural learner at all. He’s in the Navy now and lives with post-its reminding him of what to do. Especially making sure he has all the parts of his uniform!
My other kid is likely high function autistic. All the markers like sensitivities, somewhat anti-social, fixated on things. Luckily his quirks are well accepted in his field of computer programming and while he’s messy at home I think his mind is orderly!