about my beliefs. He claims he is an atheist, he studies developmental and evolutionary biology. He also suspects that I believe in spaghetti and unicorns (?), whatever it means.
Let me just concentrate on the most "important" (at least to some people) question: does God exist ?

For me personally the question if "God exist" is simply ill-defined. Consider the word "exist", Webster's dictionary definition gives: "to have actual being, be". What it means? For me, not much. We just replaced a word "exist" with "be". Some people like to discuss "do we exist?" as well. They can do that, although I'm a big proponent of using the word "exist" only in a context (in fact it is a secondary definition in this dictionary). We say "between any two real numbers, at least one more real number exists". We can also ask if real numbers exist ? If so, where "they" exist ? They are part of our universe, dreams or what ? (Hint: they exist in a set of all sets) The same reasoning we can apply to God: where could God exist ? The answer is pretty obvious to me today: God exists between any two real numbers... in hell :P