I think I might have an inkling what you are going through, though my situation is not nearly as bad. I became very ill two years ago, and had to leave a successful career. At the time, I was also fighting the medical system to get them to take my symptoms seriously. I went from being a mountain marathoner to being unable to climb a flight of stairs within a few months. The whole thing was unbelievably traumatic, but I did eventually get a diagnosis. I had three operations, and am now well on the road to recovery. While my condition wasn't nearly as threatening or scary as yours sounds, the whole experience decimated my life and my self-confidence. It also left me very isolated - while friends and DH have been brilliant, they have lives to get on with, and when I was at my worst, the days just dragged terribly and I felt so lonely and like I was nothing more than a burden to everyone around me.
I bloody hate the school of positive thinking that is all 'find the silver lining'. I want to say that up-front, because there is absolutely nothing that is nice about being ill. It's awful, destructive, hellish being in pain all the time. It's nightmarish having your life taken away from you, not some kind of spiritual epiphany! So when I tell you about what I did next, it's not with a sense of 'I'm so glad this happened to me'. I'm not glad! It was 'orrible!
Anyway, after some thought, I decided to try to build a new career as a writer. It's something I've always wanted to do, a dream I've always had but never had time or confidence to fulfil. Because I have nothing to lose, it felt like I could just DO IT and to hell with the consequences! And guess what? I think I might be getting good at it! I've had a couple of things accepted for print, and I'm now writing a non-fiction book on philosophy too.
It does mean that we have considerably less money than we used to do, but we don't have a big extravagant lifestyle or lots of needs, and I get up each day and feel like I'm doing something I LOVE for eight hours. Instead of regretting my job as I used to, it's given me a new life, new interests, a new voice and I hope (eventually) a new identity. It feels weird having such a change at the grand old age of 37.
The other thing the illness gave me is an understanding from the inside of what it's like to be chronically sick and disabled. I don't think anyone can quite imagine what that's like until it happens to them. As a result, I'm now getting involved in more activism around this issue, because I now can feel how unfair it is to expect people who are terrible unwell to be able to fight things like challenges to their benefits. (I was lucky enough never to have to use that system, but I often wonder what would have happened to me if I hadn't been so fortunate).
I hope that hearing someone else's experience is helpful. In spite of everything the illness has done, you've survived and that in itself makes you a strong, special, unique person. The talents you had before won't have vanished - you just need to find new outlets for them. You still have bags and bags to offer your friends, family and the wider world, it's just that it might take a different form than it used to from here on out.