Will he be tried by a military tribunal or a civilian court?
What is the penalty for treason during time of war?
I would guess that he would be tried in a civilian court since he “really” is not in the military. Our military is set up to have a civilian Commander in Chief.
The sentence for treason is “hanging”.
My preference would be to prosecute all his enablers, give him immunity as long as he testifies. For a pathological narcissist it would be hell to have to constantly have to verify that he is a fraud. Also it would remind him that he was nothing but a tool, without these enablers he would be the lazy nothing that is his true self. It would be a walking hell for him and far more punishing then prison.