I’ve heard prophecy teachers forever talk about the time gap between pre-filled and fulfilled prophetic events, and this looks like another example of it. I am confused, however, about your timing for the fulfillment of the New Jerusalem being at the beginning of the Millennium instead of the end especially since the Old Testament scriptures say the Lord will rule from Jerusalem.
A careful reading of Rev. 20 shows that Verses 7-15 are a parenthetical insert that John used to carry the dispositions of Satan and the unbelievers to their final conclusion while he was on the subject. Then in Rev. 21 he returned to the beginning of the Millennium to describe the New Jerusalem, home of the Church. There are several clues in the text that support this view. First, Rev. 20:7 begins, “when the thousand years are over” indicating that John has skipped to the end of the Millennium. Second, Rev. 21:1 is a direct quote from Isaiah 65:17 where the context is clearly Israel’s Kingdom Age, aka the Millennium, and third the first 5 verses of Rev.22 are a summary of Ezekiel 47, which is also about the Kingdom Age in Israel. And then there’s the mention of the trees growing a different fruit each month in Rev. 22: 2. This reference to time is also in Ezekiel 47:12 and confirms that John was not talking about eternity, which by definition is the absence of time.
In my opinion the view that Rev. 21-22 are about our eternal state after the Millennium, though popular, is incorrect.
Also, The Bible says that both the Lord and His Church will abide in the New Jerusalem (Rev. 21:22-27) and both the Lord and His Church will reign on Earth. (Zech 14:9, Rev. 5:10). How this will happen in not explained, but that it will happen is clear.