What is the ruling on saying, "If you leave, there's no coming back," and "By Allah, I will divorce her, and by Allah, she will not enter this house," and does divorce occur by threatening with it or by setting a deadline, such as "You have half an hour, either you leave the room and tell me you have become an ideal wife"?

You are experiencing obsessive doubts, and this makes you vulnerable to more of them. If you seek a fatwa from someone you trust and they rule that the divorce did not occur in the cases you mentioned, then you may act upon their fatwa. Repeatedly asking and moving between muftis increases confusion, so completely abandon that and stop reading divorce fatwas until you are cured of the obsessive doubts. Do not pay attention to any future obsessive thoughts regarding divorce, for the divorce of one afflicted with obsessive doubts does not occur, even if a clear declaration of divorce is uttered by him.