Did the early Christians (prior to Nicaea, for the sake of argument) believe the divinity of Christ? For the most part, yes.
With the exception of the Ebionites, and Nazoreans, whom I suspect were founded by one or more of the 72 sent out by Jesus to preach prior to His last journey to Jerusalem, and who believed in a Messianic figure within a strict Judaic concept. These followers became marginalised as Jerusalem Christianity established itself under Peter and John, and the Gentile church emerged through Paul and other apostles.
I don't think so. There would have been 20 plus years under the Jerusalem Church (James, Peter, John) to "set them straight" prior to the killing of James and the razing of the Temple. So an important point would be to flesh out what precisely the expected Messiah was "to be." If we take Bar Kochba as reference, perhaps the Messiah was anticipated to be a human that commanded authority blessed by G!d, at least that is how it would appear to me that orthodoxy anticipated the "Warrior King" Messiah as I see it sometimes interpreted (think along the lines of King David). But I think the interpretation presented here of the Nazareans and Ebionites falls on speculation that doesn't really line up with common understanding of the followers of Jesus or with cultural historical norms. First, why would Jesus personally send missionaries to deliberately misinform recruits?
His Divinity was already known or at least strongly suspected among his inner circle prior to the mission you mention. So unless these two early Churches changed opinion from Christ's Divinity to non-Divinity, it wouldn't make sense - and I see nothing to indicate this took place. Further, as I mentioned, there was at least 20 years after Jesus' execution for the Jerusalem Church to "correct" any deviance from what they experientially knew to be correct. With all the effort documented arguing with Paul, who spent decades abroad among the Gentiles, one would think that far more intensive effort would be spent shepherding those flocks closer to home. Ergo, the Nazareans and Ebionites were a LOT closer to the source than any flock started by Paul.
That said, I see nothing to indicate either the Nazareans or Ebionites denying the Divinity of Christ. The source of that Divinity may be in question (whether inborn or bestowed - though I still fail to see where it matters as long as Messiah is Divinely Blessed), but that He was Divine was not a matter of doubt among those early congregations.
And I still hear crickets around here regarding the Church at Glastonbury, said to have been founded by Jesus himself along with his uncle Joseph of Arimathea - and recognized as such by the Vatican, which is why the Bishop of Glastonbury was accorded special status as representing the oldest Christian Church.