I'd definitely try the melatonin and the weighted blanket.    One of our boys does both of those 


Does your son like it dark when he sleeps, as in pitch black?    Our son that had trouble sleeping likes it dark, he basically has a tent over his bed just like the one in the picture.

Not sure where my wife got it but I found the pic here,  https://www.privacypop.com/products/the-bed-tent?selectedOptions=%5B%7B%22name%22%3A%22Size%22,%22value%22%3A%22Twin%22%7D,%7B%22name%22%3A%22Color%22,%22value%22%3A%22Starry%20Constellation%22%7D%5D&utm_source=google&utm_medium=cpc&utm_campaign=%5BG%5D%20-%20Smart%20Shopping&utm_term=%5BG%5D%20-%20Smart%20Shopping&gclid=EAIaIQobChMI0Kin143B7QIVwP_jBx2thwu3EAQYBCABEgIej_D_BwE