Why does the WT say that the Kingdom is a government when it is much more and includes the people who are citizens in the Kingdom?
Jesus has always been the Head of the Christian congregation.
Has the WT changed it's teaching about Jesus having returned in 1914 as an invisible Spirit?
Is He going away to come again or what, how does that part of it happen in JW theology?
Nevertheless the OT saints will be in the New Jerusalem with God and the Lamb when it comes down out of heaven to be on the earth. Is there another New Jerusalem which stays in heaven or is God staying there with the Lamb when said He wants to be on earth in Zion forever?
It is large according to Revelation and would be located where the Old Jerusalem is I imagine. I see no problem for God to do that. The Bible does tell us that it comes down to earth from heaven, is that not true?
I find every kingdom / government has citizens and God's kingdom has citizens or subjects as found at Psalms 72:8 ( citizens from sea to sea - earth wide )
www.jw.org has Not changed about Jesus' return being an invisible spirit person.
Yes, Jesus went away, and John 14:19 says the world would see Jesus No more.
So, Jesus' return (Luke 19:11-15) would be invisible, only perceived seen by the mind's eye.
I don't think you calculated the measurements about New Jerusalem as found at Revelation 21:15-17 ____________________
That city is a perfect 4 square cube shape 12,000 furlongs or about 1,380 miles in perimeter surrounded by a wall 210 feet high.
The city would end up towering 350 miles into outer space.
And what about the building materials as per Revelation 21:18-21________
New Jerusalem's broad way is pure gold like glass, and its each of its 12 gates (openings) have one pearl for each gate ( imaging the size of that oyster ! )
So, how could such a city come down to rest where old Jerusalem is. This city would cover territory 14 times as large as modern Israel.
Revelation 1 itself informs us that Revelation is written in signs, very-vivid word pictures or 16 visions, so a lot of Revelation is Not literal.