Scholar, you quote the scriptures I give. Perhaps you should quote some of the Society's scriptures to back up their argument. My dates correspond with the Babylonian Chronicles, a secular source, which in turn corresponds with the Scriptures. Your dates is according to Watchtower. It's a case of Watchtower (and Scholar) being in step while everybody else is out of step. By the way, Jer. 29:10 is important. The 70 years applies to Babylon, not to "my people."
You simply need to read all the scriptures that refer to the 70 years and these are in Chronicles, Ezra, Jeremiah, Daniel and Zechariah but if you are having some difficulty then I can list these for you. Our dates are based on Bible Chronology and your listed dates are based on secular chronology hence the difference of twenty years. The phrase 'for Babylon' simply highlights the servitude of the Jews to Babylon during the period of 70 years of domination.
And if you look up the cited scriptures, you will notice there were in total three sieges and five deportations (cf. Jer. 52:27-30). One in 605 (Dan. 1:1, 2), one in Nebuchadrezzar's 7th year (Jer. 52:28), one in his 8th year (2 Kings 24:10-16; 2 Chron. 36:9, 10), one in his 18th year (Jer. 52:29) and one in his 23rd year (Jer. 52:30).
No there were only three deportations of Jews from Jerusalem during Neb's reign and only ONE Exile of 70 years.
I would say that the Babylonian scribes would have known when Nabopolasar died and Nebuchadrezzar took over the kingship.
A normal expectation of history
Translated chronicles of the Neo-Babylonian Empire appear in the following: C. J. Gadd, The Fall of Nineveh (London: British Museum, 1923); D. J. Wiseman, Chronicles of the Chaldean Kings (625–556 b.c.) in the British Museum (London: British Museum, 1956); A. L. Oppenheim, “The Neo-Babylonian Empire and its Successors,” in ANET; A. K. Grayson, Assyrian and Babylonian Chronicles, Vol. V: Texts From Cuneiform Sources (Locust Valley, New York: J. J. Augustin, 1975)
The said scholar is familiar with these sources.