Atheism Survey

I am so far atheist, that I don't even feel I need an argument to be atheist.
God is for those cute girls that like babies.

Much the same: I don't even see any need to discuss it.
I see religion as a once useful but now outdated hypothesis that doesn't sufficiently differentiate between cosmology and specific societies.
I see little reason to attack religion except to defend oneself. I do see among the many reasons to attack socialism and marxism the fact that they encourage religion and superstition by increasing general anxiety, ignorance, and poverty. Religion fades as prosperity and security increase -- one of the truths the Chinese grasped in less than 40 years.

Your question, as I understand it, is
"Why, although you were brought up by devout parents and teachers, living in a society that equals religion - however ridiculous - with respectability and punishes irreligious behavior, what kind of reason do you have to fall from the faith of your childhood and become a societal dropout, an atheist? And advertise it?"
Well, some people have a bad start.
Especially in your part of the world with 80% believers in holy books...or in, say, Yemen, sporting a similar percentage of devouts.

In the rest of the more developed world there are lots of people who, as children, were never confronted with the concept of god and sin and heaven and hell, and who, growing up, never felt the need for such an awkward construction, too busy understanding the world with their minds and senses. They simply never start believing .
I know quite a few of those lucky guys (mostly former East Germans, some Scandinavians and a few officially Buddhists here in Singapore), they're good sports leading perfectly normal lives, with high moral standards, tolerance and empathy towards others. Pretty un-neurotic, too...
Do you really think they need a reason to be like that?

The folks with the "bad start", a religious upbringing, they need reasons to end the habit of believing as they're getting older, bolder and more educated.
And a long and winding and thorn-spiked path they have to go.

Under US - or Yemenite - conditions it's neither respectable nor PC to be an infidel or a, beware, denier of god. Questioning this part of childhood beliefs is not encouraged.
Every kid in Christian societies some time finds out there is no Santa Claus. A clear sign of a rational mind. But you are not allowed to say "I don't believe in god" - like that.
No, you are requested to bring hard reasons, and if you find them in the library,
(Just the short list: Cosmogony, Geology, Archeology, Biology, Genetics, etc)
you are confronted with the "mysteries of the supernatural", which means all your rational thought is in vain because there's something super. No reasoning against super. Takes you years to elaborate that the supernatural explanation does not explain the writing of books with rules given by that super being. "Ah, but the rules are pivotal! No moral without them! Babylon!". You find out that Babylon was a (for its time) hi-tech urban community misunderstood by the few rural Israelites who did not assimilate to it. Babylonian society was based on Hammurabi's Code, 282 published laws that did not leave any room for irresponsible behavior. You find out that practically every society in history is based on reciprocal behavior, the "Golden Rule".
You find out that, in this and other points, you're lied to by the same people who told you not to lie. On closer inspection you find out that the religious community you grew up in cooperated with tyrants of all sort, actively supported slavery (for unbelievers, of course), took an active role in genocide (again, of infidels), and overall intends to send everybody else to hell... salvation's flip-side is damnation for all the others.
The only new bit in Christianity compared to old testimony is "love thy neighbor". And exactly this bit makes it impossible for a sensible juvenile to send everybody else to damnation. To love thy neighbor one doesn't have to be a christian. Just love and respect him and hope he'll do the same. Reciprocal behavior, or, if you prefer the philosophical argument, Immanuel Kant's "Categorical Imperative". That's societal, not religious stuff.
Parallel to that process you experience the development of your sexuality, and you find out everything your religious betters tell you about it is not true. Not a word. Experimenting with sex does not make you sick or neurotic or violent or loony. Not having sex does, or the feeling of guilt if you "perpetrate". Remember, we're talking about love and responsibility here. And you better check your US abortion and STD rates against mundane Sweden, Germany or Singapore before you object. No Sexuality outside of wedlock does not work. Non-believers know that and take precautions. Christians don't, and their abortion and STD rate (and the rate of very young mothers) is significantly higher.
Later, one reads Hobbes' "Leviathan", and Locke's arguments against it, and the declaration of independence, and all the fine arguments that destroy Hobbes' justification of the "absolute ruler" (Which is basically, that all men can't be trusted as they're selfish and lawless, so law has to be imposed on them by said ruler, who's above the law, of course, like god).
You find out that the people who brought you up and planted their rules in your kid brain are in really bad company, politically speaking. The Pope and Hitler, Cardinal Spellman and the league of central and South American dictators...
Now, I think, this was the final point where I personally decided to skip the polite appearance of a believer.
That was 40 years ago. I've never regretted it.
I've survived two hopeless medical conditions and two armed conflicts, accompanied both my parents to their deaths and buried them in a respectable and dignified way, and never missed the hollow christian words of comfort or the consolation of prayer.
My life is as it is, and I love its fullness in both heights and depths. I am subject to no one, and no one interferes except my peers.
Does this answer your 5th alternative?

Yes, there is absolutely no credible evidence for God, gods, supernatural beings, deities, idols or the Flying Spaghetti Monster! But my reasoning goes beyond that to your #3, where all of the 5,000+ living religions have a "holier than thou" attitude toward the others and think that theirs is the only credible religion. Then there's the problem of a "compassionate" god allowing pain and evil to exist as rampantly as they do. And why would this all-powerful Christian God have to "give up" his "only begotten" son through some bizarre ritual to "save" mankind? Religions, Christianity particularly, have fought science tooth and nail throughout their sad existence to suppress the advancement of science and learning!. The intellectuals within their societies have been tortured, burned at the stake and ostracized as heretics for their open and honest quest for knowledge and explanations of the real world around them. What amazes me is that 1st century myths, traceable to much earlier "pagan" mythologies, can have been perpetuated into the 21st century! We need Dawkins to prevail... a second "Enlightenment" to open up the potentials of mankind for its optimum growth and enrichment without the obstructions and outright impediment that comes from the religious camp. No more false beliefs and outmoded belief systems!

RELIGION FAILS, SCIENCE PREVAILS!

Darwin was a keen observer and theorist and his theory is PROVEN beyond a shadow of a doubt. The only reason it is still called a theory is because it can't be proven in the same way a mathematical theorem can. That is a problem with semantics, NOT the science!