Does a divorce and the other accompanying phrase occur for a husband who swore to his wife by saying "علي الطلاق" (upon me be divorce) due to her problems with his sister, and is the expression "تكلم ذباب وشها" (the flies on her face spoke) a metaphor for causing a problem?

You uttered two oaths: by Allah and by divorce. If you fulfill your oath and do what you swore to do, then nothing is incumbent upon you. But if you do not do it, then an expiation for an oath (kaffarat yamin) becomes incumbent upon you, and a divorce (talaq) occurs, according to the more preponderant opinion among scholars. Shaykh al-Islam Ibn Taymiyyah chose the opinion that divorce does not occur if the one who swore did not intend to effect a divorce, but rather intended to deter, prevent, or encourage, and in this case, only an expiation for an oath is incumbent upon him if he breaks it.