Is it permissible for my wife to confront my father's 70-year-old paternal uncle?

Your father's paternal uncle is considered your paternal uncle. However, the husband's paternal uncle is not a mahram to the wife. Therefore, it is not permissible for her to uncover her face in front of him, nor for them to be alone together, due to the general evidence for hijab, such as verse 59 of Surat Al-Ahzab, and the Prophet, peace be upon him, saying: "The in-law is death." The term "in-law" includes the husband's relatives, such as his paternal cousin. The Permanent Committee has issued a fatwa stating that it is not permissible for a woman to uncover [her face] to her husband's paternal uncle. However, it is permissible for your wife to speak to him and inquire about his well-being, without shaking hands or uncovering her face.