I would definitely do an elimination diet and get him on an absorbable form of magnesium ( there are liquids and powders plus adding epsom salts or using mag oil will help), omega 3 fatty acids, b vitamins, zinc, probiotics and a quality multi vitamin.
Gluten, dairy or other food intolerances can cause everything from behavior problems to autoimmune disease. Keep in mind that even after quitting these foods, it can take a year to heal the gut with the right supplements. Not a quick process.
Also look at sleep patterns. Record his sleeping at night. He is most likely not getting quality sleep even if he's sleeping for many hours.
Can you find an integrative medicine dr or functional medicine dr? There is an underlying cause just need to find it.