have all of them already happened in history, and thus, are they not "set" to happen again in the future?

Shalom, Thank you for your question. In relation to negative prophecies, we have a rule that if the Jewish people repent, then the prophecy can be nullified. Also, it is perhaps true that some of the prophecies have come to pass already – for example in the holocaust. With this in mind, it is difficult to say whether “all of them” are not going to happen in the future. Blessings.