‘scholar’:
common sense would dictate that the 70 years would have not some 'fuzzy' beginning but a distinct event in terms of history and chronology
Insight on the Scriptures, vol. 1, p. 205:
The Babylonian Chronicle B.M. (British Museum) 21901 recounts the fall of Nineveh … Ashur-uballit was trying to reconquer [Harran] after having been driven out. This record is in harmony with the account relative to the activity of Pharaoh Nechoh recorded at 2 Kings 23:29, which activity resulted in the death of King Josiah of Judah (c. 629 B.C.E.). This text states that “Pharaoh Nechoh the king of Egypt came up to the king of Assyria by the river Euphrates”—evidently to help him. “The king of Assyria” to whom Nechoh came may well have been Ashur-uballit II. Their campaign against Haran did not succeed. The Assyrian Empire had ended.
Note that JW literature calls it 629BCE because of their broken chronology, but it actually identifies the specific event in 609BCE when Babylon completely conquered Assyria, exactly 70 years before Babylon was itself conquered.
Now… when were those 7 years of Nebuchadnezzar’s alleged insanity? Remember, no ‘fuzziness’…