Well I am not a doctor. Have you seen any improvement since starting?
If you do the 10,000iu and he starts having any adverse reactions or new symptoms, then stop or change the Vitamin D back to the amount you were giving and come back here and tell me.
If he takes too much then it could cause hypercalcemia. Those symptoms include feeling sick or being sick, poor appetite or loss of appetite, feeling very thirsty, passing urine often, constipation or diarrhea, abdominal pain, muscle weakness or pain, feeling confused, feeling tired and bone pain. If this happened you would have to cease the Vitamin D and wait until he is better. There is no permanent damage, things would return to normal.