Is a husband sinful if he does not prevent his wife from uncovering her face in front of non-mahrams and from going wherever she wants, in order to preserve his family and daughter from divorce, especially since they live in China?

The wife's family is not entitled to stipulate conditions that entail a forbidden act according to Sharia, because such conditions are void for contradicting the husband's headship (qawamah). The husband must uphold the limits of Allah in his home, so he should not permit his wife to go out for a forbidden purpose or to a place of suspicion. He must also oblige her to wear the Sharia-compliant hijab in front of non-mahram men, and not to display her adornment to any of them. The wife must obey her husband if he commands her to cover her face in front of non-mahram men.