Religious texts sent by God. And nothing created God, he created everything.
There's no certain answer for second question. Because every individual is different, some may understand God's existence without texts maybe, but some may not understand it too. You can think and you can ask smart, interesting or silly questions without reading texts. But then you don't know in which era of history you living, in which era of history you are thinking. Questions you've asked, asked before you too. You may like to check/read this maybe; http://umcc.ais.org/~maftab/ip/pdf/bktxt/hayy.pdf
In this very interesting book, Hayy is symbol of pure reason-pure human, but there's Asal and Salaman too, and there's society.
You can call religion smelly dogma, and yeah, in some ways, some religions are smelly dogmas, full of clashes, full of irrationalist thoughts. But i don't think my belief is dogma, but some people can make it a dogma too. It depends on every individual's point of view.
And yeah, maybe as you said i may not have thought enough about this stuff, but since i've read a lot of religious/philosophic texts, i have the heritage of centuries, heritage of generations. And that's why i don't keep repeating questions that asked thousands of years ago.

