I had the CD of this...brilliant stuff.
His reason for
ten is one I can agree with, going with the number 10 being the interval between sets of numbers. You heard him, it was psychologically pleasing and all.
I also think the Commandments are just another type of code of law, and the writers wanted to be specific about the types of behavior, but stay general enough. Prohibiting "dishonesty and unfaithfulness" would be cover too wide of a field, with too many subjects in between the blanket of the whole thing.
Oh, and the first three for religious purposes.