Tell your son to be persistent--both with trying to get into the reach school of his choice and securing the waiver! My son's persistence paid off in both areas.
My son sent a letter to the reach school (one much like a letter of application for a job), highlighting his strengths and desire to attend the school. He attached a copy of his activity sheet and his letter of NROTC offer.
And, don't forget, there is an option to transfer the scholarship to other schools on his list, as long as there is a slot open. He could contact the recruiter of the unit that is his next choice to see how quickly that unit fills up.
And, even if he decides to transfer the scholarship to another school on the list, be persistent there. As scholarships are offered, slots fill up, but sometimes students don't get accepted to the school or ask for transfers. Making it known to the unit's recruiter gets your son on that unit's radar. Again, persistence pays off.
This is a very anxious time, I know, for your son and you. If he REALLY wants something, he has got to show it!
You can PM if you want.