If the problem is Biblical interpretation, which can often be a murky area fought with dispute, maybe it is time to move onto the realm of the astronomical observations. There is little room for interpretation in hard numbers. Otherwise, we are talking in circles.
For instance, I’ve yet to see how Cyrus was called into account for his iniquity, where as the last king of the Neo-Babylonian kingdom was, or how utensils from many chapters later were involved. Therefore, I can't see how Jeremiah 25:12 points to anything but 539 BC as the end of the 70 years. Nor do I see any other date for the first returnees, but Tishri 538 BC from reading Ezra 1 to 3.
However, the astronomical diaries help us find the absolute dates by tying events in history to a cluster of observations that sometimes occur only once every few thousand years. That is how we derive 539 BC as an absolute date. Without it, we could not fix any date in the Bible or history. The same methods can help us derive the dates of Nebuchadnezzar’s reign and from that we can derive when Jerusalem was destroyed.