I can't really add any advice to that given by others but didn't want to just read your post and run - I'd like to add my moral support to that from so many with experiences of caring for and loving people with dementia-type illnesses.
We both had grandparents that had dementia. My better half's nan would repeatedly ask him if he liked his mum's house (he grew up there, lived there all of his younger life) - after telling her the facts a few times and the question coming again he would say "yes, it's nice isn't it, what do you think of it" and let nan talk shit for a while discussing anything (not all relevant but hey ho). His nan also got very paranoid that everyone, including her daughter (his mum) and her husband, were stealing from her or thinking about stealing from her.
My nan went through a period where humour worked and she would giggle at her many delusions. We would answer some of her questions with 'love lies'. She thought my brother was one of our cousins (50-60 years older than my brother), she often thought I was my sister. She became dangerous indoors and we had to disconnect her gas cooker. Nan would talk to anyone pre-dementia and this continued during her illness. Once my cousin visited with her family, sat drinking tea for half hour or so then my nan said "this has been lovely dear, but who are you?" She would've invited strangers in. My brother handled things differently and used to make nan laugh so much she'd wet herself - then she would ask for help to clean up while having the raving giggles that this had happened. The only thing that remotely registered for nan was mention of her long-term lover (50-60 year relationship) - he had died from Parkinson's a few years previously but if I said "he's waiting for you" she'd smile and say "so I'll be with him again". Even in her last few weeks, I sat by her bedside, talking and she would only show any signs of recognition when he was mentioned. In the minutes before her death I told her she'd be with her lover, neither would have Parkinson's or dementia and they'd be young again and get to have their other life together etc. I like to think her troubled mind found some peace in my 'love lies' and fictional perfect afterlife. It hurt that she didn't always know me and who I was but I could cry later - what mattered was keeping her calm, peaceful and to ease all that confusion
I hope you can find some coping strategies and the support you need to help in caring for your dad. It is such a cruel illness that all anyone can do is try to be as kind and patient as possible. Please look into the links and agencies people have suggested - you need to look after yourself in order to best look after dad & for dad
@Bracken28 ... Oh, and if this was your first post here, welcome to Gransnet - people on this site tend to be quite supportive, so feel free to post if frustrated, need to sound off, ask questions, just have someone tell you it'll be OK etc