Vidqun:
Jehoiakim, son of Josiah, was king of Judah (Dan. 1:1). Zedekiah was the last king. How likely is it that Nebuchadnezzar destroyed Jerusalem in 607 BCE, before his victory over the Egyptians in 605 BCE? He wasn’t even king yet. His father died in 605 BCE.
Your assessment of the early Neo-Babylonian period is correct, but JWs insert 20 years into the Neo-Babylonian period after Nebuchadnezzar’s reign, pushing back the years assigned to his reign. So it’s not as simple as querying Nebuchadnezzar’s conquest of Jerusalem ‘before’ his victory at Carchemish. What we, and all of scholarship for the period, know was 605 BCE, historical revisionists like ‘scholar’ and other JWs call 625 BCE.
The Watch Tower Society vacillates between ignoring the problem - not attempting to defend 607 for decades - and occasional dishonest attempts to defend their view (like in 1981 when they said VAT 4956 was defective and unreliable, or 2011 when they said VAT 4956 completely supports their view). The fact is that the JW position is indefensible, so after JW apologists’ paltry attempts (such as their easily refuted claims about VAT 4956) at justifying their doctrine fail, they just fall back to the unbiblical mantra of ‘70 years of exile’. They don’t really care about the actual facts because of the powerful delusion connected to their end-times beliefs.