I'm a bit younger than you but sometimes feel the same way, but 75 seems more reasonable than 65. There is an interesting article in The Atlantic that makes this argument called "Why I Hope to Die at 75." (https://www.theatlantic.com/magazine/archive/2014/10/why-i-hope-to-die-at-75/379329/).

I don't have the mobility issues you have but do have some likely permanent limitations from cancer treatment. I am cynical of doctors after my experience. Most of them follow a script for all patients regardless of individual needs. However, it is still possible to find a doctor that I call a "diamond" who treats you like a unique person vs. just another cog on the assembly line. I have one. He believes me, listens to me, and does things that are in my best interest. It makes a HUGE difference. You need to find a doctor like that who can truly help you. It may take seeing 3 or 4 doctors before you find one.

For me, for now, I want to continue living because it's spring and it's beautiful outside, I want to keep writing music even if no one will ever hear it but me, and I do volunteer work that helps others a lot. Can you do something like swimming or just being in water to help with your pain? I'm just a random guy on the internet so don't know much about you beyond what you said but I do think you can find a doctor who will help you vs. just pushing pills and sending you away.