This account, as great as it is that you are happy, is not at all a good representation of Atheism.
I can tell you right now, you were an atheist for the wrong reasons. To be an atheist because you think it will answer your questions, couldn't be further from the truth.
The whole reason most people ARE atheists, is because they don't find the answers given by the bible to BE truth. They want the answers, and the only people brave enough to search for them are Atheists.
Now there is a definite line between Atheist, and Anti-Theist. You sound like you were more of an Anti-Theist. Their main objective is to cure the world of what they feel is the "theocratic disease".
They most likely feel hurt or imprisoned by their old religious ways or teachings, and wish to help free others from the same fate. In all, their outward appearance is the opposite of their goal.
Now to answer your question. The word Theory seems to be controversial in the minds of people who are too lazy to define it properly. Dictionary.com gives one definition of "guess or conjecture."
...You'll notice how this is the 7th and final definition of the word. This is because they are defining it how society uses the word. There is a term for it that I do not know off hand, but it is well represented in the word Gay. It used to mean happy, now it means homosexual.
The word Theory, is correctly defined, in the scientific sense, as "a coherent group of general propositions used as principles of explanation for a class of phenomena: Einstein's theory of relativity."
Even the bible would fall into the category of a theory by this definition. All it states, is that the theory itself, explains a phenomena. It does not state whether or not it is testable, or even correct. To say that something is disqualified just because it is a "theory" is to say that all things cannot be trusted. Not even gravity is proven 100% of the time, and is considered theory. However we all know gravity is real.
This is not the same however for the Big Bang theory. There are multiple theories how the universe started. This is just the one that scientists feel makes the most sense. The "Creation Theory" is another. Using the word theory as an argument, just shows your lack of knowledge for what the word actually means.
Now by the same assumption, I feel you assumed that every scientific anything was just a THEORY, and gave it up for the "answer". Sure, christianity can tell you why something happened. But that doesn't make it true.
Now, I have a BIG problem with the last sentence in your question, and it just shows how ignorant christianity has made you. Multiple scientific studies and experiments have shown that GAY MEN SHOW CELL DISTINCTION FROM STRAIGHT MEN, and I will link to that in the sources section. There was also a case where a boy got his penis cut off by a fluke circumcision. He was given HORMONES and TAUGHT TO THINK AND ACT LIKE A GIRL. He still LIKED GIRLS. He was then informed that he was a man and killed himself, because he couldn't stand being a man in a woman's body.
If this isn't proof that being gay is NOT a choice, then there is no hope to convince you otherwise.
This kind of ill information is the sole reason why "I" am an Atheist. All things answered by religion, just make life boring and meaningless. I personally do not wish to spend my time worshiping a malevolent dictator. If you choose to, and it makes you happy, that is your decision.
To say that children are not more susceptible to ideas than adults is just wrong. It is proven that children are more willing to accept preposterous ideas. aka tooth fairy, santa clause, easter bunny. As soon as they realize that these things are fake, they move on with their lives.
I've just done the same thing with religion.