I have no further comment regarding the 607 BCE and the 539 BCE date. I will have to do some more research on that subject.
Now regarding Daniel Chapter 4:
YoYo, there is no "double fulfillment" of any prophecy given in Daniel 4. The words are clear: Daniel interpreted Nebuchadnezzar's dream as a prophecy that would be fulfilled upon Nebuchadnezzar. It was fulfilled. End of story.
Is that all there is to the matter? There is no basis for doubt that Nebuchadnezzar’s dream of the heaven-high tree was prophetic, it being inspired by Jehovah God. But is the dream’s fulfillment limited to that ancient fulfillment on the person of one man, King Nebuchadnezzar, for him to learn a lesson regarding rulership? Is it through his personal experience that the purport of Jehovah’s dealing with him is achieved, namely, “that people living may know that the Most High is Ruler in the kingdom of mankind and that to the one whom he wants to, he gives it and he sets up over it even the lowliest one of mankind”? (Daniel 4:17) By setting up over the kingdom of mankind “even the lowliest one of mankind” does the Most High God set up over mankind the lowest grade of rulership over mankind? Evidently not! (Daniel 4:36, 37)
So Nebuchadnezzar’s dream must have a further fulfillment.
The heaven-high, life-sustaining tree of the dream symbolized the UNIVERSAL SOVEREIGNTY of the Most High, Jehovah God, particularly in its relationship with our earth. This Universal Sovereignty is eternal, “to time indefinite,” for all generations.
For a long period of time Jehovah’s Universal Sovereignty was represented here on earth. This was by means of the kingdom of Israel. Specially with King David.
King David had the sacred Ark of the Covenant of Jehovah brought into the city and placed in a tent pitched near his royal palace. Thus, as it were, Jehovah began to reign in Israel’s capital Jerusalem, and the Israelite king was said to sit upon “Jehovah’s throne.” (1 Chronicles 29:23; 16:1-31) Repeatedly King David acknowledged Jehovah to be his heavenly King, the real Ruler of Israel. (Psalms 5:2; 24:7-10; 68:24; 145:1) Certainly, then, the kingdom centered at Jerusalem with David and his royal descendants sitting there on “Jehovah’s throne” represented Jehovah’s Universal Sovereignty with reference to our earth.
In the dream, that all-dominating tree was chopped down. True to that dream, Divine Sovereignty as exercised through the line of Davidic kings at Jerusalem was chopped down, toppled, put out of operation. When? When Nebuchadnezzar of Babylon brought destruction upon Jerusalem and its temple and carried off its last enthroned king, Zedekiah of David’s family, into exile to die there. Jehovah himself had the symbolic tree of sovereignty chopped down, for he himself used Nebuchadnezzar as his “servant” to bring about this overthrow. Jehovah himself took the responsibility for overturning this visible expression of his sovereignty toward our earth. (Jeremiah 25:8-11, 17-29; Ezekiel 21:22-27).
For how long was this debased appearance of Jehovah’s Universal Sovereignty to continue? For “seven times,” which were prophetically illustrated by the “seven years” of Nebuchadnezzar’s dethronement for him to live like a beast of the field.
So my question to you is, how much time do “seven times” cover?