Moses doesn't sacrifice his son, I think you're misremembering the Binding of Isaac, where Abraham was asked to sacrifice his son Isaac(or his other son Ishmael according to Islam) to God. He is ready to, but then an Angel stops him at the last second, as all that was needed was the proof of belief. This is intended to show that believers need to be ready to give up everything they have for God, but also that God will not take things from us unnecessarily. It also contrasts God's care for His followers with the pagan gods which would accept human sacrifice, especially of firstborn children, in the rest of the near east. However, I agree with the rest of your point. God is a justification to them, not a real being which we are to love and understand. He is distant and unknowable, but very angry to them.