Magic, I just want to acknowledge that its not always possible to leave a marriage despite the common held belief nowadays that it is.
I met my husband at 16. Im almost 59 now. We separated when I was almost 56. We are not divorced and its highly unlikely we ever will be. We have no contact with each other.
It took me 10 years to leave and like you I had something to think about very carefully before making a move. I understand everything you are going through but what stuck out the most is the fact you are quite often getting angry. It happened to me as well and I became a really horrible person - its not something I'd want for you. You deserve way more, and all the more-so considering you aren't in the best of health. Is that a suggestion that you leave your husband? No, its not. But it is a suggestion that you try to find some form of help for the anger you are quite rightly feeling and expressing right now? It will be better for you now, and in the future, regardless of which future you chose for yourself.
I'll never be able to say 'thank god I got rid of the bastard', celebrate having a very different life to the one I thought Id have at this age , or take comfort from the fact my husbands life is now a mess of his own doing. The truth is that it would be honest to say separating has been all about swapping one sadness for another even though I'm now happy and I do have a very good life.
I hope some of this makes sense to you as one older woman to another in life long marriages who both had/have things to think about when it came to their long term plans. My thinking involved a severely disabled son for the most part but there were other considerations also.
I wish you well today, and in the future, no matter what decision you come to. 