When I set about this task for my OH who had PD, a friend said I should build in time for myself - that I would not be able to do it long term if I did not have some space.
So I did - I employed a friend to sit with him on set evenings so that I could go out and recharge my batteries. As he got worse, professional carers were needed, and then a nursing home. But I did find that building in time to let go was critical for me - it meant that I did not put my life completely on hold, which helped me through. The idea was that I would be able to pick up the threads of my life when I no longer had full responsibility for his care. This did not quite work out, as lockdown was upon us when he went to a nursing home and subsequently died.
I too feel concerned about your OH's approach. He is indeed right that you should accept how she is - nothing is going to change that she is totally unappreciative of what you do for her: but all the rest should be open for discussion. Should she be living with you at all? Can you cope with that? How can you divide up the caring tasks fairly? How can you build in time for yourself with no caring responsibilities? How can you future-proof the arrangements? - looking for care options for when she gets worse. Could you employ a carer once a week and both go out for the day as the weather improves and lockdown is eased?
You do not have to do all this - you can discharge what you feel as your duty in ways other than being basically her sole carer. Sharing the load is a different way of doing what you see as your duty.
A Carer's Assessment from social services is your right. Unfortunately the assessment no longer seems to carry with it positive consequences - I found this out when I insisted on having one, hoping that some money towards help might be forthcoming (as it used to when I was a social worker in adult services) but the sw admitted that it would not, and that it has become basically a paper exercise to tick a legal box. I would love to hear of other people's experiences of this.
This current arrangement is not working for you, and it is not a dereliction of duty or of your love for your OH to say so and ask to discuss new arrangements.
How many tablets do you take in the morning?
Is a new relationship possible without sex?
Is it rude to not finish a book club choice that was selected by someone else?
When a political leader lies on their CV - can you trust them?


I have had mixed experiences with the carers assessment too. I found the more professionals I got on board, the more social services listened but none of this is easy or straightforward. Over the years I have also found it often down to how good your social worker is or what sort of social worker they are. I'm sure they all work hard in very stressful environments though - I certainly wouldn't want to do it.
