I consider myself an atheist, and find my stance perfectly sufficent for explaining the world around me.
Your "God experience" could be also explained on purely psychological terms, whatever it was.
I don't think I'm alone in the universe, there's at least one planet full of life to accompany me. And even if I felt alone on some higher level, I don't think that inventing a Big Brother sort of being would be the best way to alleviate any such "loneliness".
World seems perfect to you because you evolved to fit on this world.
A statement: "there's a reason for everything" is equally viable as the: "there's no reason for anything". There's no evidence to support any one of them, but one can always use the Occam's razor, which seems to favour the second one, as the world seems perfectly able to exist without any reason to it, at least in my opinion.
There's no real reason to believe in Occam's razor's infallability, of course.
How did everything start? Hell if I know. It could very well just start. Whatever you mean, life, the universe and stuff.
I like the religion's tendency to tell people to do good, athough ideally, a human should be able to do good without it.