Re: "Matthew, Mark, Luke and John and modern scholars trace all four to a single document."
There is a hypothesis that there is a single source, but the idea that the source is a document has no evidence. There isn't a single shred of manuscript evidence or references to a single document. It is likely that a single source was the events themselves.
It's notable that the theology of the 'gnostic gospel of Thomas' is not found in the theology of the churches established by Thomas on the Malabar coast of India, which were pretty well isolated from western church influence for a long time. It seems clear that it's a forgery, and not an actual account of Jesus's teachings from Thomas.
Re: "As far as the "ant-nicean" church, Gnostics made up a large portion of early converts and some of the leadership of the early church."
Your statement seems self refuting, as Gnostics were never part of the church and could hardly be considered converts to a theology they rejected, especially in light of scripture that calls them antichrists.