I'm not completely certain what you are arguing here.
Forget my dubious original comments about Jesus' linguistic ability. The main theme I want to address is largely that which you refer to in your last paragraph:
Objectively, we don't really know anything very much about Jesus' background, social standing or education. The gospels were all written much later than he died and were very thoroughly Greek in nature. There is some evidence that Christianity is a syncretism between Greek religious ideas and Judaism.
This all follows on pretty well from the text from Ecclesiasticus which I quoted. Traditionally, Christians have liked to assert that the New Testament, and Jesus' ideas and teaching were a direct culmination of all matters referred to in the OT (and there is a deliberate attempt in Matthew's gospel to emphasise the Jewishness of Jesus). However, given the difficulties of translation referred to by Ben Sirach*, and the Hellenistic nature of much of the gospels themselves, it can be inferred that no such seamless transfer of doctrines, let alone theology, can be asserted.
You yourself know only too well how such matters have dramatically influenced the Nativity stories. John's gospel in particular, apart from a few curious anomalies, is permeated with Hellenistic thought (and the book I mentioned to SteveH "The Homeric Epics and the Gospel of Mark by Dennis McDonald" suggests likewise.)
And when we come to the (generally regarded) authentic letters of Paul, we see another version of the same problem. Though he makes many references to Old Testament details, his basic doctrines seem to jettison just about every significant teaching of the OT except two: the Original Sin of Adam and Eve, and Abraham's "Justification by Faith".
In other words, I think we agree on rather a lot.
*"You are urged therefore to read with good will and attention, and to be indulgent in cases where, despite out diligent labour in translating, we may seem to have rendered some phrases imperfectly. For what was originally expressed in Hebrew does not have exactly the same sense when translated into another language. Not only this work, but even the law itself, the prophecies, and the rest of the books differ not a little as originally expressed."
Ecclesiasticus