Is it permissible to estimate the value of the food items the wife took from her family's house and pay it to them as kaffarah, after her husband swore by saying she would be "like his mother and sister" if she did that, knowing that the oath was made in a moment of anger?

A man's statement to his wife, "You are like my mother," can signify ẓihār (a pre-Islamic form of divorce by which a husband would liken his wife to an unmarriageable female relative, rendering her unlawful to him) or something else. If he intended ẓihār by it, then it becomes a conditional ẓihār that takes effect upon the fulfillment of the condition. If ẓihār has occurred and you wish to keep your wife, it is not permissible for you to touch her until you have performed the expiation mentioned in the Holy Quran, which is: freeing a slave; if one cannot find a slave, then fasting for two consecutive months; if one is unable to do that, then feeding sixty needy persons. Returning what the wife took does not nullify the ruling of ẓihār; for ẓihār occurred the moment the condition was met and is not dissolved except by expiation.