There is no "right" or "wrong." The Trinity is a) valid, both biblically and theologically (even though the term, itself, is not present therein), and b) the orthodox stance.
The Trinity isn't about "multiple gods." It's a way to describe the one God.
That's what the Trinity says: God is One God.
That's not exactly a fair comparison to make, because a) Moses didn't write any of the Pentateuch, and b) the viewpoint at that time was henotheism -- not monotheism, so "Moses'" perspective of the "oneness" of God would have been completely different from ours in the best case.
No, they don't say that at all. The doctrine of the Trinity says that God is One. Unequivocally.