Numbers 31, 32, & 33

Why is Israel righteous to destroy the people of Midian? How does this relate to our ability to follow God well? When do the ends justify the means? How does the spoils of war get treated in relation to God's providence? Why would Reuben, Gad, and the half-tribe of Manasseh want to settle outside the boundaries of the Promised Land? How was God faithful in all this? Why does Moses retell the events already written down? How does this push for the Israelites' responsibility for the future?