>1. Why would nature deem it necessary to put the idea of gods and heavens into man’s mind if our minds were purely material? Nature never does anything unnecessarily. It would never waste energy in vain.
That's easy to answer. Religion, ideology, community, teleology, these are things that unite men and encourage them to work together for causes bigger than themselves, thus giving them a competitive advantage over those who live for only selfish pursuits. This is why throughout history things like atheism and nihilism only happen in short, isolated bursts; they simply have less staying power.

>2. Can you provide another example of an organism working against itself? The human mind notoriously works against itself by filling people with negativity. I understand fear and doubt are useful for survival but getting anxiety while trying to find a mate when you want nothing more than to mate seems like a contradictory force at play here. Why would my mind not be 100% supportive in all endeavors?
I'm not sure what you're getting at here, but most anxiety comes from uncertainty in stressful situations. Your hormones are running to get you to do something, but your mind isn't sure what the right course of action is. I don't think that's contradictory per se, because uncertainty is just a fact of life and there's always an advantage in considering multiple options.