Thank you for the replies. To respond to a few points:
The value of the joint home if the spouse is going to continue to live in it isn't taken into account for care costs.
It's the "if the spouse is going to continue to live in it" bit that worries me. I live in a very rural area that is not really suitable for older people (no public transport, amenities, etc). Would this mean that if I needed to move, then I would only have a third of the value of the house to buy myself somewhere to live? That would buy me literally nothing.
I know I seem fixated on the care home issue, but this is a massive worry for me as issues with relatives with dementia dominated our lives for a long time. Both DH's parents were in care homes because of this; his DF had a larger proportion of assets in his name, which were therefore counted 100% for the purpose of care home fees.
As for what he is saving for, he is focused on saving for retirement. He is only a few years off it (there is a 13 year age gap between us). However, he will have a good pension (another discrepancy between us: his work has a far better pension scheme than mine does, and I couldn't hope to be in the same position as him, financially, on retirement).
Protecting the deposit made sense at the time, when we were younger and not married, but after 22 years together and rather older, I feel in a vulnerable position with this arrangement. The subject came up recently, but he fobbed me off. I found it really upsetting that (at worst) he seems not to care that I might be left homeless if he were to need to pay for a care home or (at best) thinks it an abstract and unlikely possibility that does not merit consideration.
As for whether the house work is essential, unfortunately it is. Our roof is now dangerous, and the 1980s kitchen is literally falling to pieces.
In terms of legal advice: does anyone know what kind of solicitor I should contact? Family law?