You are taking God's explanation of events as literal from the world's perspective--but these things are about His ways which are higher, and not as perceived. As I have explained:
In the world (as in Adam) each event comes as Paul explained, "each in his own order." Which is obvious for each in birth, but he was referring to our death and entering into Christ. But in the case of Christ Himself entering into God--these are not of the world, and therefore there is no millennium regarding those events between Christ and the Father. When He went to the Father, He rose above the earth and above that timeline of such events. So, if you want to claim that "It is finished" did not fully occur at His resurrection, but only when He ascended--then great, that much is true. But beyond His ascension and leaving the worldly timeline...what you are seeing and basing your position on, is only of the world. But if you consider yourself not to be of the world, then it is not good that you continue speaking in those terms of the world, but renew your position to the terms of Him who has already enter in. Until then--indeed, there is a millennium between you and Him who is True...which need not be.
As for explaining the timeline in the world as if the Master has delayed His coming (as those evil servants say)--these are the times of the gentiles, that other fold which Christ must also bring. But just as He is the End and only came at the end of that first fold of Israel for whom He first came; He also being the Beginning, also only comes at the beginning of that other fold--for the cross is the apex, once for all. Thus, by faith those of that first fold were saved by looking forward believed in the promise of His coming--and then He came. Likewise, those of the other fold of the gentiles, look backward, believing that He has come already. Which is to say, that although the world perceives these events as not being finished--nonetheless, "It is finished."
And so it is written of Israel, that first fold, and told to Lot: "Escape for your life! Do not look behind you nor stay anywhere in the plain. Escape to the mountains, lest you be destroyed.” And yet the opposite foretold of the gentiles: "Look behind you, O Benjamin! (sons of the right hand)."
