Hi @Felixcat, my husband and his siblings very near fell out really badly as the younger two were doing all they could to ensure their mum stayed in her home. As she didn't like carers coming in, my brother in law was doing most of the the looking after. It worked for ten years until her dementia became more advanced, and carers were finally arranged. She accepted them really well as they were good at understanding how to persuade her to accept personal care etc.. At that stage my husband was keen for her to move into care as he thought it was awful she was alone in a house for so long not even being able to understand how to switch the lights on and off. His younger siblings thought it would be cruel to remove her from the house where she'd lived so long. In the end the care company said she needed more help than they could provide and she did move to care. She seems to be thriving.
Can you try and see if your dad would accept going to a care home for some respite and see how it goes? As for a crisis, I think it will be very difficult to prevent one happening. Your dad could decide to go out for a walk in the middle of the night or have a bad fall and not be found for hours.
This is a tricky stage where the person with dementia can state their preferences very clearly, but doesn't realise how much help they really need.