How are weighted blankets made? I never heard of them before. A quick search indicates they're used with autistic children and children and adults who have sensory processing problems. I find this very interesting because I prefer heavy covers on my bed, I sleep better and if I don't have heavy blankets on my legs they often hurt. Anyhow, I don't really know anything about them.
ETA: Has he ever slept well? I think my GS was about 5 before my daughter got anywhere near a full night's sleep and he has Asperger's. I hope you aren't dealing with something like that.