What about all of the unethical actions in the Old Testament?

This is an excerpt from the Apologetics Study Bible. 

• Narratives describe what happened, not what was necessarily approved.

1. We assume wrongly that if a story is in scripture, it must be "what God wanted."
2. Biblical narrators dealt with the real world, with all its corrupt and fallen ambiguity.
3. Shouldn't mistake realism for ethical approval.
4. OT stories challenge us to wonder at God's amazing grace and to patience in continually working out His purposes through such morally compromised people.
5. OT stories challenge us to be discerning in evaluating their conduct according to standards the OT itself provides.

• The Conquest of Canaan

1. Must be understood for what it was.
2. It was a limited event. The conquest narratives describe one particular period of Israel's long history. Many of the other wars that occur in the OT narrative had no divine sanction, and some were clearly condemned as the actions of proud, greedy Kings or military rivals.

3) An eye for an eye is remarkably humane

• Metaphorical, not literal
• Not a license for unlimited vengeance, but the opposite; it established the fundamental legal principle of proportionality.
• Punishment mustn't exceed the gravity of the offense.

More OT ethics resources:

Peter Williams on the ethics of the Old Testament here.