1. Well, it is if you believe in Bayesian probability, but then the results depend on your choice of prior - so computing a probability doesn't tell you anything other than what your preconceptions are. So then it comes back to your point #3.

2. Sure. (Although as per the anthropic principle, the conditional probability of the universe producing humans given that we are sitting here talking on livejournal is 1.)

3. This is the important point. It seems likely that most atheists have a mostly empiricist conceptual framework which doesn't consider deities at all (but does not necessarily rule out their existence). Since I've never been religious, nor able to understand what spiritual/religious feelings might be like for others, I'm not really in a position to speculate about the kind of conceptual framework that religious people have. I will say, though, that I'm far more attached to my rational empiricist mindset than I am to any specific position on whether or not there is a God.

(N.B. using terms 'rationalist' and 'empiricist' as vague colloquial terms here, not in their meanings as philosophical jargon.)