Bob, with all due respect, please allow me to suggest that your grandson's intuition about his fitness for service, may be superior to your intuition about what he really needs to do.
There is a distinct possibility that were he to enter service, the outcome may turn out to be far less desirable for your grandson and you, now and in the future, than were he not to enter the service at all.
I speak from the standpoint of having had an experience in a nearly identical situation nearly three years ago with a grandson of my own, at a time when I felt the same way about him as you do now about your grandson.
A few on this board will recall my situation.
Please accept my best wishes for good luck in navigating what may turn out to be a pretty complex situation.