The date of Jerusalem's destruction can be and has been verified by archeological evidence from multiple sources covering different empires, what is certain is that 607 BC is not the date. It is unfortunate that the stones have cried out and rebuked your 1914 calculation.
Regarding Cyrus since you mentioned him, most of his conquest we gain knowledge from extra biblical sources, which would be what type of methods used for verification.
Below is an interesting discussion about the archeological evidence that destroys any notion that 607BC could be the date of Jerusalem's destruction.
it is audio only for my Jehovah Witness students. Listen to it, Yes it is crushing
but take notes chase up the historical evidence included in the discussion, prove to yourself that another doctrine, another date has been cast into darkness within the Kingdom Halls.
Enjoy, if you are not running out of the Hall already.
