I am really struggling with the idea you have taught that New Jerusalem will not be on the earth. Here’s an alternative. If New Jerusalem is in a “Spiritual state” and not a solid building type of thing, I believe it could exist right here on earth and not be seen by earth dwellers (and they would not be allowed in it at any rate). I agree with your idea that the thing would be too large to be on Earth if it was a solid block 1400 miles square and tall. I really believe that we as “Spirit People” will be in “Another Dimension” not presently enjoyed by humans except those like The Apostle John who saw all of the tribulation events and the New Jerusalem “In the Spirit”. Have I gone off the deep end?
Remember, the resurrection/rapture are physical in nature. The spirits of dead believers will be reunited with physical bodies, and living believers will be transformed from mortal to immortal but remain physical beings. We’ll require a physical dwelling. Also, the nations will bring their wealth into the New Jerusalem and it will be a source of light for Earth. (Rev. 21:24-26) All these things suggest a physical presence for the New Jerusalem in the proximity of Earth.