I looked after my late OH for a number of years. He eventually died in a nursing home as his care needs were so high by then.
Throughout the whole of this time I continued to pursue things that were important to me - choral society, running a choir, being a school governor. I paid people to come in and be with him at those times.
I had worked in social work for many years and watched carers being crushed by the task, so made a conscious decision not to let that happen to me.
There is more than one way to care for someone - you can do it yourself and go under, or you can get help in, so that you stay sane. You are no good to him if you are burned out and becoming understandably resentful. You need some life of your own.
I have not missed your post in which you say he will not countenance reasoned discussion about the situation and he wants you on tap all the time. But he cannot have this without destroying you - and he has no right to do that.
I know this might all sound quite hard-hearted; but you can love someone, have great sympathy with them and care about their well-being without allowing them to crush you completely. That helps no-one, least of all your OH.
Just set up a chance to go and do something you will enjoy - present it to him as a fait accompli, and ask him if he wants you to arrange for someone to be with him while you do this. Once it becomes routine, he will get used to it. It is not wrong to do this - it is necessary.
I have never once regretted my actions since my OH died. I know it was the right thing to do. The social contacts I maintained have been the mainstay of my life since his death. Your OH has had a serious illness, but you know he is capable of normal behaviour because he can do this with friends.
You must start prioritizing your well-being too.