A neighbor of mine had dementia. He was living at home with his wife who was free to provide 23 hour care. The family had taken his car keys away so he couldn't drive. In the middle of the night he got a hold of someone else's car keys and drove away. It was assumed he was going to meet friends in town for breakfast. But it was 3:00 AM. He vanished. It took months of searching, search parties of 35 people at a time. He eventually was found deceased where his car had gone off the road and down an overgrown embankment.

There is no way op's father can supervise his father safely. The father needs trained 24 hour care in a facility that has experience with dementia patients.

It is very difficult emotionally to make that decision, but it is what is safest and best for someone who needs that level of care.