@lg2688
I think you may need a doctor or team of specialists to determine what his issues are, then they would work to suggest a prescription med or meds that fit his issue.
I was told there are over 100 types of dementia, so doctors attempt to custom fit the cocktail of drugs to patient needs.
Try to get a diagnosis, working with his regular doctor, a neurologist or Neuropsychologist, a Gerontologist, etc.
Good luck to you. 🌻