Why Would God Give Us an Unclear Book That Condones Awful Practices?

Questions about why God would give us an unclear book that condones awful practices, and how we can know that commands for the Israelites to kill all the inhabitants of a city were truly commands from God rather than from men who falsely attributed their own commands to God.

• If Christianity is true, why would God deliver it to us in a book left up to so many interpretations and that condones so many awful practices?
• How can we know that commands for the Israelites to kill all the inhabitants of a city, including women and children, were truly commands from God rather than from men falsely attributing their own commands to God?