If I'm understanding your quotes above correctly, I agree. The Lord's Day, or the Day of the Lord is the beginning of His millennial reign. John was caught forward in spirit to that time Jesus receives His own throne in Rev 4:2 some 2000+ years future, and shown thee viewpoints according to:
Rev 1:19 Write the things which thou hast seen, and the things which are, and the things which shall be hereafter;
Correct, the day of the Lord is the millennium.
Rev.4:2, speaking to John, John's future.
Rev.1:7
He cometh with clouds, and EVERY EYE shall see Him...
Rev.1:10 he was here on earth...told him to write these things to the churches, Future.
Warn them, thus prior to the millennium, was to write what he saw.
Past, present and future.
As you see here in Rev.4:1, John went up to heaven spiritually.
You have the seals which are the knowledge of the trumps that are about to sound.
Example:
Rev.5:10
Hast made us unto our God, kings and priest and we shall reign on the earth.
Rev.11:15,18
The kingdoms of this world are become the kingdoms of our Lord, and of His Christ.
Give reward to the saints...
Rev.20:4,5
I saw thrones, and they sat upon them, and judgment was given unto them, and saw the souls that were slain for the witness of Jesus, for the word of God, did not receive the mark, they lived and reigned with Christ a 1000 years....
On such the second death hath no power, but they shall be priests of God and of His Christ, and shall reign with Him a 1000 years.
So by my understanding, we become priests, AFTER the tribulation.