Impossible situation with no way out?

[Gilmorebrats]

I feel like I’m in an impossible situation and there is no way out, not even suicide.
For context I have had a lifetime of MH illness and eating disorders so I’ve posted here even though it is also a relationship issue.
Id be interested in people’s opinions but please don’t be too brutal as I’m very fragile at the moment.
Basically, I’m struggling to make the decision of whether to separate from my partner of 25 years. He is the only person in my life but he can be cold, moody and manipulative. He keeps saying he will change and I think he genuinely means it at least some of the time but he always slips back into the same behaviour.
He also expects me to run our lives which is exhausting and I feel like I am being used because I have all the stress and he just comes along for the ride. He moans that we are driven by my lists but we wouldn’t get anything done if it was left to him.
The downside of leaving him is that I would lose our lovely property and our animals and I can’t bear the thought of rehoming them and not knowing if they are happy and being treated well. Even if I did kill myself and leave him there, I can’t trust him to look after them all well as he doesn’t notice when they are ill or injured and forgets to fill up their water bowls etc.
He is also showing signs of dementia so I’m worried that no one will keep the animals safe if I’m not there.
I’ve tried ignoring the way he treats me but it’s hard to have any self respect when I’m letting him treat me badly and when I think he just uses me for an easier life. If I stay at least I have my animals and my garden but he fills the house and outbuildings with broken crap so we constantly argue about that. He agrees to get rid of it and then goes back on his word so it’s a vicious circle.
If I leave and we sell the house (which would break both of our hearts as we have devoted so much to getting it to its current state) then I would have plenty of money to buy somewhere nice but I would have no purpose in life. I have no friends or family so I would really just cease to exist. I don’t think I can rehome our animals but it seems extreme to put up with so much for the sake of some farm animals.
We thought of extending to have separate accommodation but I really don’t think I have the energy to go through that and he would be no help at all with dealing with all the stress and issues that would inevitably involve.
Sorry that is so long. There really seems like no solution and I’ve lived in this limbo for years, unable to make a decision.
Any observations or suggestions would be appreciated.

We have horses and all yards we've ever been at have hired regular staff. It's quite normal.

There's also Wwoofers, HelpX, Workaway and Worldpackers...

It is hard but i think you need to focus on letting go of the life you have now, and grieving it. Many of us have stayed in unhappy marriages because of kids, animals or finances. But it wears you down, you turn into a shadow of yourself because the bad relationship takes your confidence. You said you spent the day bingeing because of an argument with him. That's not healthy.
I got divorced 5 years ago and i've kept the family home because of the kids and i have a good job so i can afford it. But i'm tired. I'm now downsizing because i want a life away from reminders of him and i want less outgoing so i can maybe get a lesser job role and have less stress in my life. I also have heath issues and i can no longer look after the property. So its the end of an era of a big house, nice holidays, car etc and i have grieved this. But now i've given myself time to get used to the idea i'm actually looking forward to finding a smaller house and starting a new life.

You need to be ready to change though. If you dont like any of the options open to you its because your not ready to change anything. You sound quite angry that he may now initiate the split. Sometimes we spend a long time moaning about how awful life is but it will only change when your ready to make it change and take one of the ways forward that have been talked about here.

Good luck

So there is your solution. Buy him out & he will have the money & time (as confirmed sale) to find somewhere else.

You say he does nothing for the animals etc anyway, so you are already doing everything on your own. I expect your life will become easier.

I’ve spent the last few days sleeping and bingeing after a big argument about his hoarding.

This really stood out for me, because I was the same when I was with my ex. I put on a lot of weight, which he also disliked. I used to binge eat and drink wine because I was so overwhelmed with all his stuff in the house, and having to do everything, while he put pressure on me to "clean up the house." I can't tell how demoralising it was to try to keep a clean & tidy house around his boxes of hoard.
He left in the end - it did turn out to be another woman, although he wouldn't admit that at the time. It broke my heart (more for my DC's sake than my own) and the day he left, I tried to force him to take as much of his hoard with him as possible. He resisted of course - there's no logic or actual need for these hoards of broken crap that they're always going to do this that or the other with "one day."
The break up hurt a lot. It still does sometimes, but god, the relief in getting his stuff out of the house. I still feel it now. In the weeks after him leaving I would text him about stuff he had left. He would respond angrily to an ultimatum "I'm going to the tip today, so I can take this along too, or hand it over to you when you see the DC at the weekend." The choice was always the tip - but he would berate me for forcing him to make a choice. He didn't want all this stuff - stuff than had been causing me distress for years - but still he couldn't quite let me get rid of it, until forced to. So weird.
Anyway, the relief of having the power to clear out the crap, and only worry about myself (& the DC) is immense. It's so freeing. I have realised how much his moodiness controlled the household, how I walked on eggshells around him.
I hope you feel the same sense of relief. You will still be able to keep animals/pets - maybe not in the same way, but you still can. Think of yourself now, and the new life you can build without him dragging you down.