I can sympathize. My former FIL was quite elderly when he began to confuse my children with his and to confuse me with my late MIL.
I tried to alert my in-laws (I was an out-law), but they were in complete denial.
He was a terror to drive with, but the "real" children wouldn't take that independance away from him until he very nearly killed me and my newborn in NJ. I declared I would never drive with him again and earned the wrath of all.
The daughters thought he only needed someone to check in on the weekend, conveniently when they were down for the weekend, They wouldn't listen to me or the other "outlaw" who took care of him. He wouldn't take his meds, he lost control of his bowels, he was like child in temperament.
It was Hell since his wife was long gone.
What a difficult situation! Our extended family has some experience with Alzheimer's, as well as with ordinary old-age symptoms, and with nutty relatives who won't stop driving. I think that as a group we'll deal with the situation sympathetically, but realistically. My mom is big on facing facts!
As far as my husband and children and I are concerned, we'll be grateful for whatever time, and whatever level of understanding, we have have with Dad. It's funny, I started getting the cold chills about his condition when Johnny Cash died, and now the full impact with President Reagan's death.
People in denial can't cope with those who have healthy boundaries.
You did what you had to do.
Boy, that was one tough situation.