Can you show how Jesus could be High Priest right now, but not yet on David's throne? If you acknowledge that He is on the throne of David, in fulfillment of O.T. prophecy (such as Psalm 110), then you might have to acknowledge that your interpretation of Revelation is incorrect.
Jesus at the right hand of the Father on David's throne right now cannot be construed as reigning with a rod of iron over the nations on earth right now. Rev. 2.26,27 says the overcomers will reign over the nations. Are the presidents and prime ministers of the nations Christians? Probably not a one of them.
Satan is the god of this world for now. How can it be said the god of this world is in the pit now? But at the end of the 1000 years he is let loose for a short while, so that makes the millennium have to be before the New City, but also after the church age.
No other option is permitted.
Actually, there is another option.
Like I said before, you may have to consider your approach to Revelation may not be correct, and that is keeping you from seeing what the rest of the scriptures are saying about the kingdom and Christ's present reign, as well as what the future holds.
Consider the following:
1. In Psalm 110, Jesus is to sit at God's right hand (v.1), He is to rule until His enemies are made His footstool (v.1), His scepter will be stretched over Zion as He rules in the midst of His enemies (v.2), the people will volunteer in the day of His power (v.3), He will be a priest during this rule (v.4), He will shatter kings and judge the nations, etc. while at God's right hand (vv.5-7).
2. In Psalm 2, Jesus is to be opposed by the rulers (vv.1-3), God in heaven scoffs at their attempts to stop His plan (vv.4-5), God sets up Jesus as King on Zion (vv.6-7), the King is given everything as His possession (v.8), the King will oppose His enemies with a rod of iron (v.9), the people are encouraged to worship the King and to take refuge in Him (vv.10-12).
3. Acts 2:22-36 and 4:24-28 and Hebrews 1:5 & 13 all quote from these two Psalms to describe their having already been fulfilled in Christ.
4. If Christ is presently High Priest, and He is, then He is now seated on David's throne over His kingdom as prophesied and promised. Even Zechariah 6:12-13 describes the fact of the Messiah's rule on the throne in the capacity of both King and Priest. David's throne and His priesthood go together.
5. In 1 Corinthians 15:23-28, Christ is to rule until His enemies are made a footstool for His feet. The last enemy is death. When He has abolished all of His enemies, He will deliver the kingdom to God in heaven. This is a point you seem to miss. Between Psalm 110 and 1 Corinthians 15, there is no other kingdom to be set up. When Christ returns, the kingdom, as it exists now in fulfillment of prophecy, will end and be given to God in heaven. No other kingdom will be established on the earth because no other kingdom has been prophesied.
Here is something to consider about Revelation: the prophecy is bookended with words about the nearness of it's fulfillment (1:1-3 and 22:6 & 10). I don't know about you, but if somebody gave me a letter describing certain amazing and cataclysmic events to take place in the future, and if it said at the beginning and end that these things will take place shortly and that the time is at hand, I would not project everything to thousands of years in the future. This was written to seven churches and I have no doubt they believed those things were all to take place soon after their hearing about them.
The problem we all have is how all of that stuff was to be fulfilled. However else you may want to apply Revelation, just don't let your interpretation of it contradict everything else that is written about Christ and His reign over His kingdom.