Sorry about your current situation. Have you tried to talk to the ombudsperson or dean about this? It seems clear cut that, if you say this is a well-established program, that the administrators would not be happy to see professors treating a successful student in this way.
Additionally, although it may feel like it, I am sure that it isn't the case that no one cares about your success in the program. Having graduate students successfully graduate and be placed in jobs they want is a hallmark of success and what administrators of the program should be striving for, even if only for instrumental reasons to keep the program going. If it really is the case that everyone you have met, especially your advisor, as you have mentioned, is neglectful and cruel to you, I would urge you to look toward other methods of social support like your family, friends, or religious group.
Lastly, about knowing what to write, if you have reached your fifth year in a well-established program and have already defended a proposal, you are a competent student that understands the literature and methodology enough to finish. It is not your fault that you are in this position and it is likely that if you were in a more supportive one, you may very well be much further along with much less stress. Ultimately, know that whatever happens, this regrettable situation isn't your fault, and we all hope that it improves for the better.