My adopted son (has SPD) and his brothers (not living with me) have all got SPD traights. One especially who has cerebral palsy was more of a nightmare at night than mine. But boy mine was bad. Use to scream and thrash all night long. Mine now sleeps in his own bed, bedroom and sleeps like a log. Not bragging, just informing. His brother needed to be ubber close to his carer. Touching all night. He is on melatonin but also went to a sleep clinic. He use to scream till he was sick if she left the room. After doing what the sleep clinic told her, he too is now in his own bed, bedroom and sleeps most of the night. He has little blips here and there. Keep trying, don't give up.
Also does your wife take him out in the day to parks, children's centres, playground. These are good for them both.