Jeffro,
As your pictures clearly show, there is no evidential proof that the event took place in 538. There are several assumptions, without evidences. I am glad you indicated the looseness with the word "possible". Little wonder the event is dated variously from 538 to 535.
Did the writer assign Nisan reckoning or Tishri, accession or non-accession? At which part of his first year did Cyrus make his decee? How long did it take the people to prepare? How long were the people settled in their towns and villages before they ventured to Jerusalem? Where is Daniel's "Darius" and his first year in all of this? Were Cyrus and Darius co-regents?
It's only a problem for the WTS, since it is a pivotal crucial date in their system.
Nowhere does the Scripture say that the 70 years ended with that event. 2 Chr 36 says the 70 years of Babylonian dominance ended when the Persians defeated them. That is simple and obvious.
Thanks,
Doug