You are mistaken. Atheism makes no claim about gods not existing. It simply rejects the claim that they do exist. This is called the null hypothesis and it is the default position. If you would like to have a legitimate conversation about this then you need to understand this difference. Otherwise you are just strawmanning atheists and that's just intellectual dishonesty.
Everybody is born without a belief in god. It should require extraordinary evidence to prove such an extraordinary claim. People just accept it because it's comforting.
No. There's a difference between not believing in god (atheist), and believing she doesn't exist (antitheist, I guess). It's not that I believe that there is no god, it's possible, I just don't believe you when you tell me that there is. Why should I?
The vast majority of people who identify with that label mean they don't believe in a god or are not convinced. Not that they are asserting that there is no god.
Me personally? I am willing to assert that there is no 3-omni personal God. I am not willing to assert that I know 100% that there isn't some weird-ass star trek like alien somewhere that has such cool tech we should properly call it a small g god. I don't think that there is one but I can't really claim that I know that.
No. Atheists being skeptical of the baseless claim that God exists makes perfect sense, the gnostic claim that God at least provides a hypothesis is perfectly baseless.