HoldingOnTight,
What you can do is Let Go and Let God. Don't believe that? Can't wrap your head around that? Do you have a Higher Power? Accept that there is nothing you can do. You did not Cause this, You cannot Cure this, and You cannot Control this. There is nothing you can do. Nothing. You are not responsible for another person's sobriety, mental health, behavior, or consequences. Your obsession with helping this person has NOTHING to do with being military. You are making excuses for your sick thinking, the way the alcoholic and the addict make excuses for their sick behavior.
The person you are talking about is a VERY sick man. If all the doctors and professionals that surround him now are unable to help him, what makes you think YOU can? You are not God. Let go of this person's problems, his outcomes; let go of the feeling of responsibility you have towards making this person right and ending his suffering. Only God can end their suffering. You have NOTHING to do with another person's relationship with God.