Lech L'chah

How can we understand Avraham's refusal of the war bounty when he readily accepted, and even anticipated, the gifts from Pharoah?
Perhaps this approach can help us. When Rashi mentions the "side effects" of traveling, in the beginning of the parshah, it seems that Hashem's brachos to Avraham was a sort of  "traveler's insurance" to avoid them. However, I believe we can understand this in a new light.
The level of absolute "annavah" expected of any Jewish leader, and ever-more so in our forefathers, required Avraham to be devoid of any hishtadlus which can lead one to feel "kochi v'otzem yadi" in building our nation. It was Hashem's specific command for Avraham to litterally take a step into self-destruction. Avraham was to free himself from any human effort in his success. This would effect the roots of his prodigy to be totally 'G-D made'.
Although the gift from Pharoah was anticipated by Avraham, there was no effort done on his part to that effect. Sarah's claim to be his sister was to protect his life. The wealth that klall yisrael inherited from Egypt without effort on their end (the slavery was not their capital investment for their retirement!) was enrooted in the gift Pharoah gave after being smitten for taking Sarah.
The war bounty, on the other hand, is understandably the payment (if not cause) for the war effort.
With this in mind, we can understand the new title attributed to Hashem at the time Avraham's refusal took place. Malki Tzeddek referred to Hashem as 'Konei shamayim va'aretz'. The One to whom the entire ownership and jurisdiction of the world is His. (see ramban, sforno, & targum for this definition.) Avraham's selflessness expressed his awareness, that our efforts are conceptually needless, opposing the common belief that G-D made the world and then left it for us to run.