#4 has a very good point, echoed by other posters: the Old Testament, while taken as historical truth by religion, is not an historical document per se. Instead, by historical and scientific standards, it is a metaphorical or subjective account, like the Iliad and Odyssey. Therefore, objective truth about the origins of a religion must be searched for in other places, such as on the ruins of ancient cities. However, one thing that is objectively known is that Judaism as a religion has been in the region for at least four-to-six thousand years, depending on interpretation.
Skeptoid, while not addressing this particular issue, has an interesting essay on the Jews in Egypt with some solid sources.