How do I deal with a 79 year old untreated, stubborn, angry in denial dad, a widower of 23 years, with stage 4 plus dementia/Alzheimer's?

He has always been selfish, a commitment phobic, a snob that uses his moral compass as an excuse to act like a miser, always would get angry he has to do anything for anyone else, compares himself to everyone, including his 2 daughters and wife. I had to get my own corrective lenses, teach myself to drive and pay for all of my own personal items by the time I was 16 as it was just nonstop "no". After my mom died from cancer 23 years ago, which he forever complains about as he had to take care of her for 6 months, which was quite easy considering she slept the whole time on chemo, he sold the house, lived alone, never committed to marriage or relationship again as he said it sucked the life out of him that he never wanted to commit in the first place. My older sister has pretty bad ptsd from being in iraq as a military dentist, she never had kids, she does not live local. I have been a single mom to two teenagers with very little help from my dad or my sister as they both hate kids. After my dad retired he would disappear for 3 years at a time to go camping using this as an excuse to not be in relationships. His neighbors complain he never socializes, and gets angry if they are nosy, and I am friends with a neighbor as I live about 40 minutes away, and she keeps an eye on him. The last ten years I have noticed decline in memory barely spend time with him as he has become quite miserable, gives me a lot of guilt trips or has a million excuses or mean comments about why he does not have healthy relationships or compares himself to me pointing out how much smarter, wiser, luckier, entitled, harder working than me. He lives in a small old impractical house that is terrible for eldercare, and like all of his generation, refusing to sell or move or downsize or deal with their decline. The last year has gotten much worse as he is being exploited by a 68 year old woman who squatted in an estate for a few years, filled the estate with a bunch of hoarding, was finally evicted by the executor. I found out about this about a week ago as the woman called the police on my Dad as he was ignoring her for a day, which I was shocked as I have seen him ignore me and his only grandkids, his sister and my uncle and his parents for years because he is "tired." My dad cannot remember how to get anywhere without GPS telling him where to go or constant reminders, he never leaves the house, and I have seen him wandering in malls or parking lots trying to remember his car or my car or what he was doing there, this squatter texts him nonstop. During the last 6 month eviction this woman manipulates my dad for hours on end, she has her own mental issues, and the estate executor had her physically removed by the authorities, she manipulated my dad to be on premises up until last minute. The two of them take all day to move a bag, they are extremely dysfunctional. The last week or so I went to find them on the side of the road living like 2 homeless people where my dad sleeps in a uhaul van and she sleeps in a really old station wagon. My Dad spends the whole afternoon and evening yelling, arguing, getting angry with her, falling, wandering, dozing off, verbally abusing people so I reported both of them to elder abuse for mutual self neglect and abuse. I also called 911 every time a fall happened as I am a mandatory reporter. My dad is condescending, rude, gives me guilt trip, and refuses to go to the doctors with me. I called 911 a few times with the falls and wandering off and the driving around, getting lost, but as soon as they show up he tricks them into going away, he gets a glazed expression in his eyes like he enjoys all of this and they leave as they state he is too decisional and no crime has been committed. He also enjoyes telling me "you lost, I won." I did convince the woman to check into a woman's shelter, and since then he has ignored her demands as he has done to everyone else in his life. I have tried to help but at my wits end.