Whilst admittedly not addressing your questions, I urge you to ask everyone likely to come in contact with him to not correct him or react in any way when they see him do it - not even help with his words. We stutters all know that there is a terrible feedback loop based on performance anxiety whereby our fear of listeners reaction fuels deeper anxiety which causes worse stuttering which causes deeper anxiety.... Also I'm m sure you're doing this based on your obvious intelligence from my reading of your letter: but get a speech therapist to look at him