Is what the husband said during an argument with his wife's sister, along with repeated threats of divorce, in addition to him telling his wife "I will divorce you" and her replying "You have divorced me," and his affirmative confirmation, considered a divorce, especially given that some of these events occurred during pregnancy?

If the husband broke the aforementioned divorce oath, namely: your brother expelling you, and his failure to do what he threatened your brother with, then his divorce has taken place upon you. The husband's statement: "I will divorce you" or "We will separate" does not constitute divorce, because it is a promise. His answer "Yes" to your question "Have you divorced me?" constitutes divorce if he intended to enact it. Anger does not prevent the occurrence of divorce as long as the husband is aware and chooses to divorce. His statement: "Each one goes their own way" is a metaphorical expression that constitutes divorce if he intended it.

The ruling on whether divorce has occurred or not depends on knowing the husband's intention, and this should be presented to scholars.

A wife informing her husband about an illicit relationship to test his jealousy is a conduct contrary to Islamic law, and a husband frequently swearing by divorce is unsound. The obligation is to live together amicably.