Is a wife forbidden to her husband merely by his saying, "You will be forbidden to me if I watch those movies again," and then he watches them again? And what should he do in this situation?

Scholars differ concerning the ruling on prohibiting one's wife. Some consider it ẓihār, some consider it ṭalāq (divorce), and some consider it an oath. If you intended divorce, then it has occurred, and you may take your wife back if the divorce has not been finalized (three pronouncements) and before her ʿiddah (waiting period) expires. If you intended ẓihār, then it has occurred, and you must offer expiation for it before engaging in marital intimacy with your wife. If you intended an oath or did not intend anything specific, then you must offer expiation for an oath. Swearing by divorce and prohibition is discouraged, as it is among the oaths of the dissolute, and using oaths to abandon sins is not a sound approach.