Thank you for your illuminating posts. I had not been aware of the disbelief that the start date was Artaxerxes decree.
If we go by this interpretation, which I believe to be true, the Old Testament does give us rock solid evidence of whom Jesus truly is, the CHRIST. Thus the claim there is no proof falls away.
They all use this amorphous fungible entity that they call Tradition [oral, rabbinic, patriarchal, Talmudic, magisterial, whatever ...] to interpret and explain away the plain and clear meaning of those Scriptures that they would just as soon like to get rid of.