What should I do about my husband's desire to commit adultery with his friend's wife, and his attempt to make his friend commit adultery with me?

A Muslim cannot accept indecency for his wife; rather, this is a form of dayouthah (pimping/cuckoldry) and wickedness. The Messenger of Allah, peace and blessings be upon him, said: "Three types of people Allah عز وجل will not look at on the Day of Resurrection: the one who disobeys his parents, the woman who imitates men, and the dayouth." Therefore, it is not permissible for a woman to obey her husband if he commands her to do so, because the Prophet, peace and blessings be upon him, said: "Obedience is only in what is good and permissible." She should advise him, and if he persists, she should threaten him with informing her guardian. If he does not desist, she should seek a divorce, as فسق (immorality/wickedness) is one of the justifications for seeking a divorce.