How do I care for Alzheimer's/dementia Dad who won't stay home and won't listen to me?

People with dementia are unable to reason. That's why your dad is unreasonable. I agree that the doors should be kept locked with locks that your dad is unable to figure out.

If he is unable to care for himself any longer I would suggest a nursing home unless your dad can afford to have someone come in and stay with him around the clock. It sounds like he needs complete supervision.

Being unreasonable is what dementia is. His brain is broken and he doesn't understand safety concerns. Have you spoken to his doctor about this ?

The only thing that I know that works is locking the doors and having the caregiver have the key at all times. I'm assuming that someone lives with him.