@Katehc,
Well this is confusing.
Who was the toxic relationship with? In your thread title you say it has been 40 years, you then detail the ups and downs with your lover. Has your lover been with you 40 years?
At any rate, to the lover you are just an extra. He can't generate the courage to tell his wife not to invite others on a vacation. You've had good moments, but, you have also had quite a few rough times with him. Maybe it's time to just leave him in your past.
Then there is your husband. Do you love him? Enough to stay with him, with no lover on the side?
As for being 65 and being worried about finding love again, you may or may not. Many people find a second, third or even fourth or fifth love when they are your age or even older. I have a friend who found a second love at the age of 73. His wife had died, he met a woman whose husband had died. They met, got along, moved in together. They're happy. Stop thinking about your age, get out and enjoy life. Happiness will come.