Hello, I am Rafael. Thanks for asking your question - I'm here to support you. (Information posted here is not private or confidential but public).
I am very sorry to know about this person's situation
What you describe here is very concerning since it shows how severe this phobic disorder has evolved to the point of him feeling overwhelmed by it, to consider isolating himself this much from the world.
As with every other mental health disorder, rehabilitation required of adequate psychological treatment. Psychiatrist could only provide drugs that could help reducing some anxiety symptoms, but would not rehabilitate him from this tough disorder. I do believe he needs intensive psychological treatment, which should start with individual therapy and then lead to small group therapy. the professional who could provide this treatment is not a psychiatrist but a psychologist with training and credentials in psychotherapy o a professional psychotherapist with expertise in anxiety disorders-phobias.
When a disorder like this, which uses to start from childhood remains untreated, it could lead to other mental health disorders, from other anxiety disorders to depression, personality problems and more, affecting mood, other psychological processes, functioning because of the challenges it presents around social settings and in relationships.
I would rather suggest looking for a program offering intensive treatment for anxiety disorders rather than getting support from a professional with a private practice only. This way he would get the best and multidisciplinary support he may require to promote the best rehabilitation chances with stable and comprehensive professional support.
Does it make sense?