KEK
Nag Hammadi are mostly Gnostic texts which I find heretical personally although some like Shepard of Hermas and the Didache are real gems. The Nag Hammadi are seperate discovery from the Dead Sea Scrolls. Not the same.
Dead sea scrolls are different and were library of the essenes and are oldest copies in the world of biblical texts. Some are likely from the Temple itself.
Jesus was an Isrealite. probably started being taught the Torah by his mother when he was 2 yrs old like all Hebrew children.
Tribe of Dan making it out to Ireland Northern Scotland possible even likely.
As far as ancient buildings marking seasons, that has little to do with defining Christianity. But having an accurate way to mark seasons and have a calendar was damn helpful then and now. Entire civilizations depended on accurate farming. Among many other purposes as well as keepers of this knowledge being spiritual leaders is reasonable. And theres the Jesus was half Alien thingy.