How do I deal with a Dad (94) whose favorite topics of conversation constantly involve cruel or embarrasing subject matters?

I am 58 years old and one of my earliest memories is of my Dad telling my mother and I how as a young man he had once visited a house where the father had his daughter and son in their nightclothes and was beating them with his belt. Over the years many more stories of this ilk followed on an almost daily basis animal cruelty, beatings he had witnessed, horrific accidents he had seen. However his most favorite subject was and still is his own beatings at his mothers hand and how he was the 'whipping boy' out of his five siblings. My mother had a tender heart and always ensured that my sister and I were always made to feel sympathy for what he had been through as a child and given what he had told us we did indeed feel sympathy. I assumed his obsession with violence came from his having been on the receiving end of beatings. However after years and years of listening to these stories my sister asked his two remaining sisters if the stories of his beatings were true. Both sisters were horrified and said no they had never ever seen him receiving any beatings, or any marks on him from beatings, sure they all received smacks back then but no more than any of their friends did. Also from their memories my Dad was in fact the golden boy of the family and had only the best! My own memories of his Mother was a loving caring woman and certainly my Dad was happy for her to child mind me on a regular basis although I do recall him telling her just before she died that she was heavy handed when he was a child a fact she denied. The thing that my sister and I find really upsetting / embarrasing though is his talk of inappropriate sexual matters REALLY personal again this has been lifelong and frankly is flesh crawling. I have lost count of the number of times he has claimed to be out walking and came across couples or homosexuals in the act of having sex all graphically described. This conversation can be on public transport, in a cafe, a lovely family meal out etc, etc. We were both brought up in a home where what he said was law and although he was a good loving father in many ways neither of us would have crossed him for fear of reprisal. Indeed despite being the most impatient man I have ever met he lovingly cared for my Mum when she was diagnosed with Alzheimers .Now my Mum has passed what I find really sad is that we were never allowed to have Mother / Daughter times together, he always had to come even on a girly day out. Even after my children were born when a girl needs alone time with her Mum I could not get time alone with her, in fact I had three afternoons on my own with her when my first child was born and I treasure them. I breast fed them and he would go on and on about how he loved to see a child on the breast, there was no way he was going to see my child on the breast that was for sure. Even the actual births was marred by him going on and on about how he would love to be in at the birth, again freaking me out so no wonder I was admitted to hospital with high blood pressure! Trying to tell him no is futile he would turn up at the house after the birth once or twice on his own which was awful for me trying to breast feed this was despite being asked very politely not to come as I needed time to rest. The same goes for his inappropriate sexual conversations telling him to stop or walking away mid sentence doesn't work, he will just resume where he left off when you return. The strange thing is he will only talk about these subject matters with me, my husband and my sister, he wont raise these topics with my brother in law though. I do love him but am feeling more and more resentful towards him so any help in dealing with his unusual behavior will be much appreciated. I have learnt much from reading other peoples problems on this website but never come across one like mine.