Well i'm sorry to say that your knowledge of what atheism is, what it entails, and what science says are ignorant at best and a straw man at worst. With atheism (
What is Atheism? | American Atheists), you just don't believe in a god, you could still be an atheist and believe in an after life or believe in ghosts but it does not entail the abandonment of these beliefs or any others for that matter aside from a god one.
Nothing before the big bang is more of a misconception and a big one in line with this theory. In a nut shell, the big bang describes the evolution or expansion of the universe from a point smaller than a proton but it does not describe or even mention how the universe came to be. Nor does it imply that a singularity (Infinite temperature, finite mass, zero volume, infinite density) is on par with philosophical nothing apparently or even exists in reality. The most coherent answer ever given, is i don't know. The fact that a singularity arises in the math implies that there is a problem with general relativity and we need a quantum theory of gravity to describe what is going on at a point so close to t=0. Heck, one planck second after the big bang is the closest we can get before all of known laws of physics breaks down.
So if you are going to make straw man claims about atheists claiming the universe came from nothing, first prove that there was literally nothing before the big bang. If you can spot the contradiction in the statement above then you can get a cookie. Philosophical nothing cannot be shown to exist as it is the absence of existence and is thus such a paradoxical & ill-defined concept that it has no meaning or fluidity in our known reality.
Take these four statements below for example:
1. Something always existed in some form or another.
2. Something came from a previous nothing.
3. There was something then nothing.
4. There was always nothing.
These are some of the only possibilities that could come to mind and some seem illogical while others impossible. "4" is quickly disregarded due to the large body of scientific evidence to the contrary. "2" & "3" seem to make the assumption that something can come from nothing and vice versa, which seems to be paradoxical in light of their basic definitions. Even if you say that god created the universe from nothing, god was something, and thus the universe came from him. If the universe even did come from nothing, then it could be argued that what we thought was nothing, was really something with no detectable properties to indicate otherwise. Thus the only reasonable answer to give is that there always existed something, whether that be god, allah, yahweh, the flying spaghetti monster, or some other more plausible answer. My bet is on the last of the list, but remember to not ever make a god of gaps argument because of the question mark that is t=0.
Also, please stop being scientifically ignorant and look up abiogenesis, the second law of thermodynamics, and chaos theory in classical mechanics. Really the universe started out ordered and will continue to become disordered. Also, it isn't really naturalism of the gaps, more like, I found an explanation that gives testable, falsifiable results and agrees with all other previous data thus making it the most likely explanation. God is not this, you just want to assume him into existence. Lastly, where does science get the immaterial from the material?
Lastly, lastly, here is a good refutation of the Kalam cosmological argument upon which I assume you are using.
1(
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2(
) Here is a fallacy built off of the argument called the Kalam cosmological argument fallacy.
This is the best I could do in short time so hope you find it challenging.