It was always my impression that Balaam had little inclination to follow the Mosaic Law, unlike the person of Eve, and was rather painted as a man mostly motivated by personal gain. I'm curious as to how his character was used as a stand-in for the Jew who was naturally motivated to follow the Law.
In both Genesis and Numbers the "speaking animal" is simply a stand-in for the Jewish conscience telling the Jew not to break any of the Ten Commandments.
Interestingly, the platonists and gnostics and variants thereafter very much insisted that "all is mental" and that the physical and sensible was but an illusion. Your conclusion that the snake of Genesis was purely a byproduct of the mind is almost identical to the conclusion of these mystical ones.
Going a little further, what the snake claims to offer man in the garden of Eden is seemingly entirely spiritual, since God is spirit. The gnostics would say that "God is mind". Therefore, indeed any actual provable physical and historical reference became unnecessary as it was besides the point.