The Inclusion and Identification of the Amorites

Exodus 17:8-16 chronicles the battle between the Israelites and the Amalekites. The episode contains odd elements. So long as Moses’ arms were raised, Israel did well in battle. When they dropped, they did not. What is the point of this action? Why is there a reference to the “throne of Yahweh” associated with the altar built to commemorate the victory? And above all, why was Amalek cursed by Yahweh for elimination?