Ilove TTATT, I mention the above not to discourage your scholarly efforts but to put the JW belief system into a context.
JW org beliefs are a confidence trick, all the talk of "God's truth" is part of the sleight of hand to bamboozle the followers. They have already decided; irrespective of whether 607 BCE is based on facts or not (they must have realized that it isn't) they are using that year as a part of their working mythology.
The acid test used by the leadership of the org is not truth or scholarly evidence but loyalty to what they have decided is "divine truth". Their cult depends on suppressing reality.