Based on what you related, I think you need to act now to start protecting him. Have you started checking out assisted living and/or memory care facilities that could take care of him? That kind of cognitive decline can accelerate rapidly.
He's one of those that says he'll never go to assisted living or nursing home. Ever. And, he doesn't want strangers coming to his house either. It's going to be a struggle. I recently talked to his doctor who said dad's not at the point where I can force him to do anything he doesn't want to do.
We are going to start checking out facilities. DW and I recently visited the local senior services office and they gave us a ton of information on different options. The counselor told us that the vast majority of people that refuse to go to assisted living only end up going after something happens that requires a hospital stay - and at that point - depending on the circumstances - they are told they can't return home and will need to go to an assisted living facility. Unfortunately, that will probably be what happens with my dad. I need to visit some places and at least have an idea of my options before that happens.