Jeffro
It is not the case that a significant majority of scholars prefer 586, but any who do are wrong. No "poblem" for me whatsoever. Even mother Watch Tower disagrees with you.
The Watchtower, 1 October 2011, page 31:
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Most scholars prefer 586 not 587 BCe. Keep up reading the WT for you may be converted to 607 BCE
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Most translations of Jeremiah 29:10 properly refer to 70 years for Babylon. Even in the rendering of the few translations that incorrectly allude to 70 years as a period at Babylon, the 70 years doesn't include the journey home, and allows the 70 years to end before attention is given to their return. But the JW interpretation is a distorted mess because they say the 70 years (which supposedly started more than a decade after most of the Jews were already in exile) ended only once they'd arrived in Judea. Worse still, in the JW interpretation, most of the Jews are in exile for over 80 years, some are in exile for less than 70 years and others are in exile for about 65 years.
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Traditional renderings favour 'at Babylon' rather than 'for Babylon' and the NWT is in very good company in this respect.. The 70 years as explained in our publications is simple and clear as the Return was in 537 BCE, the Jewish Exile lasted 70 years so it must have begun in 607 BCE with the Fall. You talk about a 'distorted mess' then you should look at the journal articles on the subject and you will see a mess indeed just like your pretty chart.
scholar JW