It is not your job to save someone. Going through my disaster of a marriage taught me that if a person does not desire to change on their own, they are not going to want to change just because you wish they would. Even if all signs point to change being a good thing, it does not mean it will ever happen.
It is better to align yourself with those who are working to improve their lives all the time but who have a good foundation already going. :) Take off that cape and save yourself.