What is the expiation for a husband swearing — by saying: "My wife shall be as my mother" — falsely to deny watching pornographic films, given his repeated action of doing so?

The husband's statement to his wife, "You will be my mother as a wife to me," has no legal consequence. A husband watching pornographic films is an abominable and extremely ugly act. There is no sin upon the wife if she inadvertently discovers her husband's actions, but spying is forbidden and one must repent from it. If the husband curses the Lord or the religion, this is apostasy, which entails the wife becoming unlawful to him, and she must separate from him if he does not repent.