The nightmares in particular are interesting to me? Did they follow a basic theme?
I have post-traumatic stress disorder, not all JW related, but three of my recurring nightmares were.
One was an evil-looking eye that stared unblinking at me from down a long corridor. As a JW I felt someone was always watching me (God, Satan, parents, elders, etc.), and I never felt good enough.
The second was about getting beaten and tortured in a Nazi concentration camp. This possibility was emphasized pre-1975.
The last was of me and my unbelieving family being engulfed in flames at Armageddon.
Sparrowdown is right. Your son needs education. After reading JW facts, Crisis of Conscience and The God Delusion, my nightmares stopped, never to return.
I had years of counseling before exiting that were worthless. JWs are taught to never speak about "spiritual matters" with anyone but elders. Therapists can't help under these circumstances.
The therapy that did help me greatly post -exit was Dialectical Behavior Therapy. It is skills based and helped me greatly in making my way in a world that was so foreign to me. It helps tremendously with identifying black and white, all or nothing thinking, teaches assertive communication and mindfulness to help with distress tolerance.
PM me if you like.
Diane