Dying for a belief does not make it valid. Nor is it the slightest bit of proof therof, or else Mohammed Atta and his 18 fellow hijackers proved Islam correct by slamming into buildings at 500 mph.
But then Jim Jones and David Koresh are right too, and what about the atheist Rosenbergs...Timothy McVeigh.and Buddhist monks who light themselves on fire....a friend of mine who ate mushrooms... and peyote and commited suicide two days later because the world wasn't "REAL"...lots of people die for their beliefs and that is not evidence of their correctness...
As for God being the simplest explanation, it actually is tied with the "scientific" explanations (ie the Big Bang, M-theory [very strange stuff about membranes touching each other and creating new universes, and theres an infinite number])
I AGREE with you that the KEY difference between humans and OTHER ANIMALS is our ability to reason. REASON is the best evidence that we are made in the image of God. Reason is the only way we can understand his creation. I AGREE that the universal desire amongst sentient beings can be taken - in some ethereal way- as evidence of a Creator. Its when you start arguing that God is ALL-POWERFUL and ALL-LOVING and ALL-KNOWING that you run into problems, because that requires a perfect world (see the Riddle of Epicurus)