You are asking a far too complicated question for me to answer responsibly. What I can offer is some thoughts for you to consider: You are in your 60s. You are considering two very significant changes in your life that will have impact on both you and your husband.
Before going ahead with either the surgery or the separation, I urge you to find an experienced therapist who works regularly with older clients and talk this through. You need input and support from a professional — especially since your husband is depressed.
Therapy is not limited to relieving mental illness. Often we therapists serve as an objective sounding board for decision-making. Often we provide support and guidance for personal growth.
As a senior myself, I’ve come to appreciate that it is sometimes more helpful to talk with an age-mate who understands issues around aging (and the life decisions that come with it) from a personal as well as a professional point of view. As actress Bette Davis once said, “Getting older is not for sissies.” Life decisions are more momentous because there is less time to make changes and less time to back away from those changes if we make a mistake.
The decisions you are making are very, very important ones. Please don’t be impulsive about them. Don’t let other people pressure you into making them before you have given them the time, respect and consideration they deserve.
I wish you well.