Although all CAHers are different and require different amounts to maintain control, your son’s dosage does seem very high.  My CAH extreem salt wasting 7 year old  weighs about 65 pounds is on the exact same dose as your son.  His OH-17P is around 90 now (which seems overmedicated to me, but the Endo thinks it’s ok considering the other numbers of other blood factors).  What is your son’s OH-17P?