I knew a couple of guys in the '60s who were sniffing a lot of glue. They wound up in an institution in a vegetative state, permanently. Glue-sniffing kills brain cells.

http://www.sacsheriff.com/crime_prev...e_abuse_08.cfm

Inhalant abuse can kill. And if it doesn't kill you, it can leave you with severe brain damage or severe respiratory problems. There's no fooling around ? even a first-time user can end up dead after "sniffing" or "huffing" inhalants.
Treatment for schizophrenia back then may have included shock treatments and/or Thorazine. I don't think there was enough published information for him to be able to fake mental illness.

Maybe after 30 years, he'll be able to retire.