General question: I've read somewhere that there's a Bayesian approach to at least partially justifying simplicity arguments / Occam's Razor. Where can I find a good accessible explanation of this?

This is a good question, but not when applied to the origin of the Torah example. There a more appropriate discussion is of the motivated cognition of the original Talmudic authors, who would have happily attributed 100% of the Torah to the same source, were it not for the 8 verses which do not fit. For a Christian these authors are already suspect because they denied the first coming of the Messiah, so one's priors of their trustworthiness should be low to begin with.