They certainly seem to be very wary of actually mentioning the 2520 years nonsense.which it plainly is, just a quick look at Daniel 4 without JW Specs on, shows that the 7 years were fulfilled upon the King, which = end of and fulfillment of the prophecy.
No way can a sane person stretch this simple "prophecy" to apply in the 20th or 21st Century
The problem with the 2520 years is as you say, 607 BCE is the one year in History where nothing at all happened. The destruction of Jerusalem took place 20 years later. So 2520 years does not bring you to 1914.
Ergo, neither does counting back 70 years from 537 BCE , a year chosen by the WT to make 607 and therefore 1914 credible, as the Searcher says, the Jews were released in 539 BCE. The only way it would have taken 2 years to reach Jerusalem would have been if they had used my local 'bus "service".
The whole 1914 thing, and the whole "The End is Near" piffle have lost all credibility in about 10 minutes of someone looking at facts on the Internet.
Come on JW's WAKE UP !