You have just had a detailed answer to all of the above (several times).
Paul does not say that anyone before him preached Jesus as the messiah. Does he? If you think he does, then please quote it!
And none of those before him (c.50-60AD) in this "Church in Christ", ever wrote to claim they had preached Jesus before Paul. Did they? If you say they did, then please quote it.
I am arguing from the "fact" of what actually IS written in Paul's letters. That is "evidence".
You, meanwhile, are indulging in pure speculation.
Incidentally - I thought you were just arguing that Paul did not even exist? If Paul did not exist then how can he tell you about what he thought a Church in Christ was once preaching?
Well, there is this:
https://www.biblegateway.com/passage/?search=Jude+1
Jude 1 New International Version (NIV)
1 Jude, a servant of Jesus Christ and a BROTHER of James,
To those who have been called, who are loved in God the Father and kept for[a] Jesus Christ:
...
17 But, dear friends, remember what the apostles of our Lord Jesus Christ foretold. 18 They said to you, “In the last times there will be scoffers who will follow their own ungodly desires.” 19 These are the PEOPLE WHO divide you, who follow mere natural instincts and do not have the Spirit.
20 But you, dear friends, by building yourselves up in your most holy faith and praying in the Holy Spirit, 21 keep yourselves in God’s love as you wait for the mercy of our Lord Jesus Christ to bring you to eternal life...
If you think of Paul as one of these "Scoffers" who is telling people to ignore the laws of Moses, it's easy to see how some people connect him with the "Scoffer" in the Dead Sea Scrolls...
http://www.essene.com/History&Essenes/cd.htm
...
The period in question was that whereof it is written, like a stubborn heifer, Israel was stubborn' [Hos. 4.16J. It was the time when a certain scoffer arose to distil upon Israel the waters deceptive and to lead them astray in a trackless waste, bringing low whatsoever had once been high, diverting them from the proper paths and removing the landmarks which their forbears had set up, to the end that through his efforts those curses cleaved to them which had been prescribed when the Covenant was concluded, and they were delivered to the sword...