Leolaia,
The question of identity is not as simple as it seems. Why? Because authority, titles and even a name can be imputed to someone sent as a representative of the one so named and/or titled. We see this with the angel in the burning bush that used the name of God, as did such angels in other verses that delivered such messages. And the expression first and last when explained the way it was can be used by another. This does not force identity as some may think. It can then be argued that the expression Alpha and Omega in all occurrences in the Revelation apply to Jesus since the name Yawheh does not appear in that scroll as it did in OT texts where even such use also did not prove a personal identity.
You covered the disputed texts very well and this should not be a problem for anyone, but even with the inserted words nothing really was accomplished. Jewish history and theology for thousands of years establish the foundation for our thinking regarding the God they worshipped not third century Christianity. So verses like the ones under discussion would not change this foundational belief in one God. (One God in three persons was not a part of this foundation).
Rev 1:11 KJV Saying, I am Alpha and Omega, the first and the last: and, What thou seest, write in a book, and send it unto the seven churches which are in Asia; unto Ephesus, and unto Smyrna, and unto Pergamos, and unto Thyatira, and unto Sardis, and unto Philadelphia, and unto Laodicea.
Rev 1:11 NIV which said: "Write on a scroll what you see and send it to the seven churches: to Ephesus, Smyrna, Pergamum, Thyatira, Sardis, Philadelphia and Laodicea."
The text that followed this explained itself and its use of words such as first and last dissolving any connection and use elsewhere for other reasons.
Rev. 1:17 And when I saw him, I fell at his feet as dead. And he laid his right hand upon me, saying unto me, Fear not; I am the first and the last: 18 I am he that liveth, and was dead; and, behold, I am alive for evermore, Amen; and have the keys of hell and of death.
The one that will come quickly is? The one that has the "reward is with me" is? The Christ! So the use of Alpha and Omega does not identify this Christ as another person in this verse and he can say this for the reasons being also the King of the city provided by God as His representative.
Rev 22:12 And, behold, I come quickly; and my reward is with me, to give every man according as his work shall be. 13 I am Alpha and Omega, the beginning and the end, the first and the last. 14 Blessed are they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city.
And perhaps the verse that started it all was 1:8 with words like Lord and Almighty. But John identifies himself as "brother" and "companion in tribulation" to this Lord. God uses son not brother to identify those that belong to Him. But Jesus did say that on many occasions and John acknowledges this relationship..
1:8 I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty. 9 I John, who also am your brother, and companion in tribulation, and in the kingdom and patience of Jesus Christ, was in the isle that is called Patmos, for the word of God, and for the testimony of Jesus Christ.
So the argument is not as simple as it seems and no doubt will continue to our very end.
Joseph