Hi. So sorry. An awful and sad situation for you. I think you did your best in a shitty situation and due to mental and physical issues,she has,which are beyond your control,things have gone sideways.
I understand because my partner has a lot of similar issues. I am hopeful the problems will be worked out and not get worse. However,if they do,I know I may need to walk away at some point. My partner has not rejected me in the manner you describe,but honestly,whether it is mental illness or willful rejection of you,for some reason…the upshot is the same. This is hurtful and it appears you have done your best and suffered enough.You are not obligated to sacrifice the rest of your time and life to a poor bet for happiness. Even her friends and relatives find this difficult or impossible to deal with.
I have personal experience of a relative that ended up homeless. It is a sad situation,but any help the family tried to give, came “to not”. Sometimes people can not or will not be helped.
Free yourself and build a better life. You can maybe still be a resource or friend and still be caring,but don’t let her problems consume you or the rest of your life. It sounds like you have done your time and tried to be/were a loving husband. I wish you well. Throw the guilt out the window. It does not/will not serve any purpose. It won’t help her and will unfairly hurt you.