Honeybears - I'm sorry you have deleted your post. You are doing your best in a difficult situation and torn lots of ways with both parents needing support.
Your reaction to your dad is normal, but he no longer understands.
Everytime people ask me about my mum, I always say the memory loss is the least of the problems, the inability to process information is far more difficult to deal with.
I think my mum's cognitive functions went long before her memory loss showed up that she had dementia.
Sadly you have to work round problems with dementia, tackling head on just leaves to arguments, which you can't win. I kept trying to point things out to my mum, and she just came up with an argument against things, so where possible I avoid confrontation.
Still haven't worked out how to get her to keep radiators turned on, 3rd winter in her extra care flat and if I tell her she just says she doesn't feel the cold and it costs money. I tried telling her she'd end up ill in hospital and she said she wasn't bothered, I said I didn't have time to visit (she understand I am busy and don't have much time) and she said that was OK as she didn't mind if I didn't visit (true as she knows I am busy and thinks she is OK to sort things out herself). Not bothered with that line of arguing again.
OH took over a year to understand that she couldn't understand things as she comes across as if she does.
But it is so frustrating.