All other siblings have left my mother, and she has turned to me. This is her pattern. How do I help her and protect myself?

I have Complex-PTSD due to years of all types of abuse from my family. I have been the stable member of a family of narcissists and/or high functioning alcoholics. My father had a legally written Medical Directive that was hidden by my mother and ignored by one of my brothers who is/was a physician. This brother was acting in erratic ways for 10 years, was fired from a long term job, and did not follow my father's DNR. My other siblings backed him, my father took all power away from them eventually, and I carried out the DNR. I had avoided conflict whenever I could with my family. My father and I were close, and all my siblings and I were successful in our professions until my brother started displaying bizarre behaviors. Like most people with Complex-PTSD, I played my scapegoat role until I watched my father suffer for almost a year. That is when memories and feelings came flooding back to me. I have been in therapy for 5 years, but I need to hear the opinions of others. My mother has had serious mood swings for 50 years but refuses medication. When she is angry, she speaks to me in a very cruel way. I have been distancing myself from her slowly. Now my brother, who was living with her, has lost another medical position and went back to his house about 70 minutes away. My personal family is a very happy, normal family consisting of two retired teachers (my spouse and myself) and my son and his wife. I realize now that I truly detest my mother who is just mean as others have described her. She lives in our family home and it is filthy. She was never this type of housekeeper until the past 15 years. She is a hoarder. I have had three heart attacks and have COPD due to second hand smoke and asthma. I never smoked. My father passed away 7 years ago, and my physician brother has slowly destroyed all my family relationships with lies because I was asked to testify against him in an ethics hearing. I did not, but I am afraid of him. He second wife, a nurse, has left him. He is my mother's favorite child. My father loved all of us for who we are. I was by myself when he died. He warned me they were all weak , and I probably would be. Recently, Mother has been ill and stayed in my house for 5 days but had not spoken to me except through cruel texts for over three weeks. We assist her financially each month, but my family and I want nothing to do with her. She is 89, but that is young for her family. Most women live by themselves until they pass away at 100 or even older. I am the youngest child, and am 63. Please help me with suggestions that are moral and kind for my mother but will protect both my mental and physical health. My heart attacks are not due to blockages but are related to stress diagnosed at 14 years old. Thank you for any help you can give me.