Bail. Neither one of you is in this realtionship for healthy reasons. You’ve been a life preserver for her as well as a way for her to avoid completely commiting to a man who loves her. She has been a physical and emotional outlet for you as well as a way for you to avoid finding a relationship that is reciprocal and mutual.
I don’t know why you both are so pessimistic about finding someone who can be in a healthy relationship with you. That’s for you to work on with a therapist. But I do know that a relationship based on this kind of co-dependency is bound to fail.
I encourage you to get into some therapy to work on why you have been willing to accept such a poor substitute for love for a dozen years. Someone as loyal and as sensitive as you are deserves better.
I wish you well.