My marriage is very similar except my husband is loving towards me. We have been married 30 years, but for over half those years we have not had sex. My husband seems to be having EAs with older women. I have found no evidence of sexual activity.
Like you I have threatened without following through for years. Now he sees my frustration as vents and ignores them. He also has developed ED, which has shut down any hope of resolution.
I feel I have a too good to leave but too bad to stay situation. We can't afford two households. It is just the two of us now. We are getting older and starting over is less certain. I too feel I missed out on intimacy and that makes me sad.
I'm attending IC to help me accept my situation. I work on appreciating what I have and letting go of the resentment of what is missing. I am working on accepting that it is and has been my choice to stay. I have to stop blaming him. I could leave if I wanted to. It would be hard, but not impossible.
I hope it helps to know you are not alone. Some men are asexual. IC is helping me. Maybe it would help you too.