Okay what exactly is Jesus said to baptise with both in the gospels and Acts?

Matthew 3:11
[11]I indeed baptize you with water unto repentance, but He who is coming after me is mightier than I, whose sandals I am not worthy to carry. He will baptize you with the Holy Spirit and fire.

And again Jesus in acts references the Father and the Spirit.

Acts 1:4-5
[4]And being assembled together with them, He commanded them not to depart from Jerusalem, but to wait for the Promise of the Father, “which,” He said, “you have heard from Me;
[5]for John truly baptized with water, but you shall be baptized with the Holy Spirit not many days from now.”

In the same Acts 2 you quoted, Peter references the Father

Acts 2:22
[22]“Men of Israel, hear these words: Jesus of Nazareth, a Man attested by God to you by miracles, wonders, and signs which God did through Him in your midst, as you yourselves also know—

He referenced Jesus in the verse you mentioned and the same verse you mentioned but cut off (I will be charitable and assume you are not being fraudulent) also mentioned the Holy Spirit,

Acts 2:38

[38]Then Peter said to them, “Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit.

So we have the trinity referenced in the very first gospel sermon in Acts 2. All of them are referenced simultaneously by Peter in the below verse:

Acts 2:32-33

[32]This Jesus God has raised up, of which we are all witnesses.
[33]Therefore being exalted to the right hand of God, and having received from the Father the promise of the Holy Spirit, He poured out this which you now see and hear.

So once again your argument falls flat. Even based on your own references.

Secondly, for Benjamin Sommer, he explicitly acknowledges the trinity is not inconsistent with the idea of God in the OT. Here is his quote (one of many b.t.w., you can read his whole view in pages 132-133 of bodies of God and the whole last chapter of that book deals with this point)

"The most obvious example of fluidity in Christian thought is the notion of the trinity. For all the trouble Jewish and Muslim philosophers have had with this notion, the trinity emerges as a fairly typical example of the fragmentation of a single deity into seemingly distinct manifestations that do not quite undermine the deity's coherence"

I never said I agree with his characterization of what exactly that plurality is (so obviously I don't agree with his idea of what the trinity is) But if there is in fact a plurality within a single God, even by way of multiple embodiments per Benjamin Summer's view, then it is not pagan for God to refer to Himself as "US" which is my initial point.