It's never too late to start over Snood.
You don't have to keep living like this unless you choose to.
Things will go downhill fairly quick I would guess from what you've described
and then there will be the "guilt factor" of leaving her when she's down
(in hospital, out of control in a visible way in public, dementia increasing, out of money, etc.) When that happens, it is actually harder to walk for some people.
It was like that for me with my mother. I should have quit enabling her drinking and rescuing her years before when she had a chance to help herself.
But I didn't, and then I felt obliged to see it out to the end.
You see the train coming pretty clearly from your posts.
Step off the tracks man--find love or at least find peace in your golden years.