Is it lawful to stop spending the night at a wife's house due to fearing her?

Fatwa no. 10686 I married twenty-five years ago and my wife and I had children, who are all married by now, except for the youngest son who will marry soon, In sha’a-Allah (if Allah wills). My life with my wife has not been at all happy for a long time as married life should be, I could not even get what a man needs from his wife. After a while, I was able to marry another woman, and, with the Blessings of Allah, I found comfort and peace of mind. I tried, as far as I was able, to deal equitably with my wives in terms of food and drink, accommodation, and nights. (Part No. 19; Page No. 197) Shortly, after my second marriage, I was in my first wife’s house and she gave me a glass of milk. I did not want to drink it myself, so I took it from her and gave it to one of my children who was sitting next to me. When my wife saw me give the glass to the child, she snatched it from his hand and did not want him to drink it. From this I realized that she had put something in the glass, but I do not know whether it was magic or poison. I became very angry and wanted to hit her, but I stopped myself because my children asked me to leave her for their sake. They said that Allah would hold her accountable for what she did. After this, I have not slept, eaten, or drunk with her, fearing that she might harm me, but I still meet all her needs in terms of food, drink, and clothing. I have not divorced her, because her parents are no longer alive, she has no brothers, and also for the sake of my children. My question to Your Eminence is: Am I sinful for not spending the night with her, or eating or drinking with her, bearing in mind that she no longer desires sexual intercourse because she is now around 60 years old.