Husband won't have sex anymore.

I don't know if I correctly understood the part about sex, for your husband, seeming to be about his relationship with the rest of the world. (If not please forgive me.) But in reading it, what immediately popped into my mind was this is a means to avoid dealing with the real issues; because if his sexuality-related problems relate to your husband's relationship with the rest of the world, well, there's perhaps not much that can be done about that, it's too big and amorphous a subject to tackle so why try?

Back when MSF was still Psych Central, Doc John had an article in the archives the title of which was something along the lines of: "Denial is a Powerful Impediment to Treatment". To my mind, the attitude your husband is taking is a form of denial in a sense... denial that there is anything that can help, so why try? And, as Doc John wrote, it's a powerful impediment to treatment and a return to a healthy life.

I'm not surprised to learn your husband is 50. That makes perfect sense to me. That's the age when the wheels began coming off the cart for me so to speak. It's unfortunate your husband won't seek some counseling or therapy or perhaps even a men's support group if such things exist where you live. But, there again, the reality is you can't save him. He has to do that himself. All you can do is do whatever you need to do to take care of yourself.

The one thing that occurs to me that might help is if you can get your hubby out-and-about more (assuming the two of you aren't already doing so) doing whatever it is the two of you enjoy doing together. The pandemic has made things extremely difficult from that perspective. But if circumstances where you live have improved at this point, getting out doing things together the two of you enjoy might help brighten his spirits as well as his outlook in general. Then, perhaps, his interest in sex may follow of its own accord. A "tangential" approach such as this may be a more effective way of addressing the problem than is trying to confront the problem head-on, so to speak. Without intending to alarm you I do fear (based on my own personal experience) that, barring some form of intervention or positive action on your husband's part, the hole he appears to be digging for himself may only deepen. (Hopefully I'm wrong.)