I use OTC generic Unisom, I can take one tablet and split it into 3 parts take a 1/3 and sleep like a baby, it is non addictive, My OB/GYN actually told me to take it when I was pregnant as it also has a ingredient that helps nausea. I think if he needs to use something temporarily to get off pot and back into a regular sleep routine that a little help doesnt hurt.
My difficult child also has trouble sleeping, Unisom does not work well for him, he takes Seroquel. But since he has been working regularly and waking up early he does have an easier time falling asleep.
Good Luck
Grace