What is the way to deal with a husband's constant doubts and ill-will, which are based on erroneous interpretations of innocent events, especially after these doubts have expanded to include close relatives like his brother-in-law, given my suffering from infertility and my family's refusal for divorce, and my feeling that he underestimates my sacrifices?

Having bad thoughts about a Muslim is forbidden. It is incumbent to think well of one's wife, as she is the most deserving of good treatment. It is not permissible to accuse her of immorality simply because of ease of penetration. She must veil herself from her husband's brother-in-law and not be alone with him. The wife should be cautious and avoid anything that would lead her husband to accuse her, and she should improve her relationship with him. As for childbearing, there is no sin in seeking divorce or khul' from a sterile husband if treatment is not possible, while weighing the harm of remaining with him without children against the harm of divorce. After divorce, the wife can offer herself to whomever she approves of his religiosity and character. She must perform Istikhara (prayer for guidance) and ask Allah for ease.