How do non-trinitarians reconcile Rev. 22 verses 6 and 16? Jehovah's Witnesses, as one non-trinitarian example, claim that Revelation 22:13 is a reference to Jehovah God and not Jesus:

I am the Alpha and the Omega, the first and the last, the beginning and the end.” 

It is spoken to John by an angel and not directly by either Jehovah God or Jesus (Rev. 22:8)
Revelation 22:6 says that God sent this angel to John:

And he said to me, “These words are trustworthy and true. And the Lord, the God of the spirits of the prophets, has sent his angel to show his servants what must soon take place.” 

The &quot;he&quot; in the above verse is the angel from verse 22:1 and 8:

Then the angel showed me the river of the water of life, bright as crystal, flowing from the throne of God and of the Lamb - v.1
I, John, am the one who heard and saw these things. And when I heard and saw them, I fell down to worship at the feet of the angel who showed them to me - v.8

Later in verse 22:16 Jesus himself claims to be the one who has sent the angel:

“I, Jesus, have sent my angel to testify to you about these things for the churches. I am the root and the descendant of David, the bright morning star.”

What exegetical proof is there that the Alpha and Omega statement of verse 13 is not applied to both Jehovah God and Jesus equally since both sent the angel who proclaimed it?  Or put another way, how can this be reconciled with a non-trinitarian belief?
Both God and Jesus can be understood to send the angel, because Jesus is at God's right-hand (Matthew 26:64) and is God's representative - God does things through Jesus.
The NT generally, and Revelation in this case, repeatedly and clearly distinguishes between Jesus and God. Jesus is the 'Son of God', Jesus says 'My God, my God'. Jesus says 'Your God and my God'. In Revelation, Jesus (= the Lamb) is repeatedly distinguished from God, such as Revelation 1:1 &quot;the revelation of Jesus Christ, which God gave him&quot;, Revelation 1:6 &quot;who has made us to be a kingdom, priests to His [i.e., Jesus'] God and Father&quot;, and Revelation 3:12 which contains this distinction 4 times in one sentence. One of the verses you quote, 22:1, is another example of this (&quot;the throne of God and of the Lamb&quot; - two different things).
Therefore, when you have a pattern of clear statements distinguishing between the two, it is poor exegetical practice to take one, unclear instance and try to draw overarching consequences from it. Instead, the author of Revelation is repeatedly drawing a distinction between God and Jesus while simultaneously drawing a close relationship between them.
So, if we take Jesus to be saying &quot;I am the Alpha and the Omega&quot; and so on, then a non-trinitarian has two obvious options. First, to say that Jesus is speaking in the place of God (as his representative, much as the angel is speaking in the place of Jesus). Second, to say that all those descriptors can apply to either Jesus or God, depending on what is meant. They are all vague titles.
So whatever exactly is occurring in this passage and whatever exactly the descriptors mean and to whom they are supposed to be applied, what is clear from Revelation overall is that Jesus (= the Lamb) and God are two distinct things.