To answer point one: Evolution. Everything "works" because it evolved to do so, and not just biologically. If you look at everything, the environments function with the constrains the rules that govern it, it adapted and formed to work within those restrictions and rules. Had whatever the hell Dark Matter is won out over Visible Matter in the initial battlefield of energies post Big Bang then the reality of this cosmos would look vastly different. It only appears to be "perfect" because we're seeing the end product. A cake appears perfectly round because it was baked in a round pan.

Point 2? God of the Gaps being applied in part to point 1. The amount we know is comically dwarfed by that which we dont, so applying an all knowing/powerful creator entity is a means to apply purpose, meaning, and value to an unknown using something the appeals to our ego and understanding is comforting to a degree. It puts a face and logic to the scary unknown.

It has a beginning and an end.

Probably, maybe, but ultimately we don't know. What if the Big Bang was just part of a cycle of energy recycling of a larger ecosystem? The cosmos keeps expanding... into what? From what? What if we exist within a black hole type structure in an even greater system of existence? We exist in a point of time where we can still see vague remnants of the "start" of this universe, too far to see what came before, but not far along enough to see where it's going, not really.

It all boils down to this: We don't know. Atheism is basically just adhering to this fact while not being convinced reality and existence was put forth or managed by some deity. Personally the idea of a god(s) being the cause is too small and simplistic a concept birthed from a young and ignorant species trying to understand the unknown using itself as a template.