How can He rule in Jerusalem from the seat of David's throne if He isnt even here?
Why are you taking that so literally? How could He possibly literally sit on David's throne in the future? Surely, it has decayed and doesn't exist anymore. We need to allow the NT to interpret the OT for us. The NT reveals things that are hidden or not clear in the OT. I accept Peter's explanation of how Jesus took His place on David's throne.
Acts 2:29 Men and brethren,
let me freely speak unto you of the patriarch David, that he is both dead and buried, and his sepulchre is with us unto this day. 30 Therefore
being a prophet, and knowing that God had sworn with an oath to him, that of the fruit of his loins, according to the flesh, he would raise up Christ to sit on his throne; 31 He seeing this before spake of the resurrection of Christ, that his soul was not left in hell, neither his flesh did see corruption. 32
This Jesus hath God raised up, whereof we all are witnesses. 33
Therefore being by the right hand of God exalted, and having received of the Father the promise of the Holy Ghost, he hath shed forth this, which ye now see and hear. 34 For David is not ascended into the heavens: but he saith himself,
The Lord said unto my Lord, Sit thou on my right hand, 35 Until I make thy foes thy footstool. 36 Therefore let all the house of Israel know assuredly, that
God hath made the same Jesus, whom ye have crucified, both Lord and Christ.
Peter indicated here that the way in which God fulfilled His promise to David to "raise up Christ to sit on his throne" was by way of "the resurrection of Christ". Peter equated the raising up of Christ from the dead with the raising up of Christ to sit on David's throne. He was placed "the right hand of God exalted" as "both Lord and Christ". As King. Jesus Himself, after His resurrection, said "all power is given unto me in heaven and in earth". Paul said regarding Jesus after His resurrection that God the Father placed Him "at his own right hand in the heavenly places, Far above all principality, and power, and might, and dominion, and every name that is named" and "put all things under his feet, and gave him to be the head over all things to the church" (Eph 1:19-22).
The way in which Jesus was made King of kings and Lord of lords was not in the way people expected because of carnal thinking. His kingdom did not come with observation (Luke 17:20) and is not of this world. The kingdom of God that He reigns over "is not a matter of eating and drinking, but of righteousness, peace and joy in the Holy Spirit" (Romans 14:17). God does not do things the way carnal men expect Him to, He does it the way He wants to do it and how He planned to do it long ago by bringing a spiritual kingdom to the world through His Son that His Son reigns over. The kingdom that we all are in right now.
Colossians 1:12 and giving joyful thanks to the Father, who has qualified you to share in the inheritance of his holy people in the kingdom of light. 13
For he has rescued us from the dominion of darkness and brought us into the kingdom of the Son he loves,