DP expecting to live with me for care when we don't get on

Just. Say. No. And mean it.

I'd remain non committal. If he's 80 now and in reasonable health it might not even happen.
Just be clear about what you are willing to do. Lots of helpful advice on this forum if things change!

Op, I could have written your post word for word, except that I've moved further on in that I've totally cut contact with him.

I was never allowed to disagree with him - mum would always say 'don't go upsetting your dad' or 'your dad's always right you know'! He was a total bully. He made mum cry. He drove me into the floor telling me my life was a pity and a shame. That I was useless and stupid, and that if only I'd done ABC I would have Achieved XYZ.

So, he says that HE is going to live with you. What about your mum then? Or is this if he ends up alone? I secretly thought for years that like you, I'd have mum live with me in a heartbeat, but not him, never him.
You really need to do what PPS have suggested and say 'that's not possible' EVERY TIME, then change the subject, walk away, whatever.

I've paid the price by not being able to see my mum anymore. I can't walk into the house as they have large locked gates that I can't climb over. If I tried to phone mum and he answered he just put the phone down on me, so I've given up trying.

I'm a few years down the line now and honestly, even though I miss my mum badly it was still the best decision for me. No more guilt tripping, I've picked my self esteem up off the floor and am now successful in my career. I am living my life. Not his.

Make a decision in your mind to be ruthless for the sake of your own life, family and well being - to mirror his own behaviour. 'No' is a complete sentence, let him sort himself out - oh and stuff his money. I had the same thing said to me -that I would be cut out of the will if I didn't do as he said. Well whoopee, I didn't do what he said and the sky didn't fall on my head. . The first time you say NO is the hardest, but then gets easier.

We are trained from birth to obey the patriarchy - It's time to rebel methinks. Stand firm.

Try not to let it stress you. He thinks he can use his will as a hold over you but you don’t care. That’s it. You’ve made your decision.

Sorry OP- it must be difficult.
He can spend the money he saves by leaving you out of the will, on care for himself. Win win OP

You need to decide NOW where your boundaries will be. Will you be taking him/them to the doctors, hospital, chiropodist, optician, dentist, hairdresser... doing their shopping, dealing with medication... etc etc etc. How much time will you be willing to give in the future, because I can assure you, from experience, that the issues will not start with care at home.

"Haha dad, live with me? Like you have your mum living with you to take care of her? Dream on!"

Try not to worry about it. You aren't going to care for him, no-one can make you!

You could always say you’re happy to talk about arrangements when the time comes but it’s not necessary to talk about them now. Maybe say there would be a lot to organise so it would be better to have those conversations when the situation arises.

That way you can keep him thinking the conversation is open when in reality you have made your decision, you’re just not going to tell him right now.

Don't say anything about it, it may not happen & will cause stress for everyone, mostly your mum. But, if it does eventually get to the situation where it becomes a reality, stand your ground. You aren't obliged to care for him.

I agree that you need to put your foot down on this one. There's a similar situation in the family of a friend of mine, and he has made his dc's lives hell for decades. Do you have siblings?

It’s just a vague thing at the moment from the sounds of it. So best just to ignore it. Otherwise you’ll end up having huge arguments about a situation that might never arise in practice.

It’s a good idea to be clear in your own mind about what you’d be willing to do, should it be necessary.

Sounds awful for you OP. Nobody should be forced into a situation like this. Next time he mentions it I would say that it wouldn't work for you and isn't an option. Repeat if he mentions it again. Lots of people have to pay for their care, it's a fact of life. He is very entitled thinking you will provide it all for free!