Welcome. I'm sorry to hear about your son. I started to suffer from migraines about the same age, well before any of the fancy drugs. My mom had the perfect remedy(or so I thought ).
She would put me in a cool dark room (curtains drawn and a sheet drawn over me with a soft pillow for my head). She would put cold compresses on my head and stay with me until I went to sleep, keeping me calm and soothed. That intense amount of pain can be scary for a child and reassurance can stop him from getting more upset.
Children's tylenol and 1/2 gravol may also help. Migraines are known to inhibit you from digesting food and medications. I find that gravol will sometimes settle my stomach enough so the medication will work. Gravol will also help him sleep and relax.
Hopefully these ideas will help a little.
The secret of health for both mind and body is not to mourn for the past, not to worry about the future, or not to anticipate troubles, but to live in the present moment wisely and earnestly. Buddha