@charles826, Have you seen this other discussion on chronic nausea?
-- Chronic nausea: What helps?: https://connect.mayoclinic.org/discussion/chronic-nausea-2/

I agree with @katgob about seeking help for your husband at a major health facility like Mayo Clinic or a teaching hospital. Are you able to go with your husband to talk with a doctor to see if you can get a referral to a specialist?