RE: How science has already proven that god does not exist.
Your idea of "proof" seems to be coming up with a "better" explanation that makes the existence of something unnecessary. Of course, "better" is subjective.
I'll help you. One definition of "better" is that used by Occam's Razor which says the simplest possible explanation is preferred for the reasons stated below.
In science, Occam's razor is used as a heuristic technique (discovery tool) to guide scientists in the development of theoretical models, rather than as an arbiter between published models.[1][2] In the scientific method, Occam's razor is not considered an irrefutable principle of logic or a scientific result; the preference for simplicity in the scientific method is based on the falsifiability criterion. For each accepted explanation of a phenomenon, there may be an extremely large, perhaps even incomprehensible, number of possible and more complex alternatives, because one can always burden failing explanations with ad hoc hypotheses to prevent them from being falsified; therefore, simpler theories are preferable to more complex ones because they are more testable. - Wikipedia
But I'm an engineer and I specialize in making things more complicated than they need to be.
One need not assume that the Designer of the universe feels any need to simplify it down to your current level of understanding.
Since we can't possibly know what the Technical Requirements are for the Universe, we are unable to state whether the most simple or "natural" explanation meets all the requirements or whether it has been over simplified due to our lack of knowledge of the true "specs".
Therefore, you are stuck with only being able to say "I have found an explanation I like "better" for nature as I currently understand it.
This, of course, proves nothing about the actual state of reality at all.
In fact science has no way to have absolute certainty of anything because all its conclusions are falsifiable. For example, when science says phlogiston does not exist, it is not for it to be 100% sure that it does not exist, but because it is more prudent to consider that it does not exist until proven otherwise. The inexistence is the rule and the existence is the exception, and that the existence of phlogiston is not necessary to explain absolutely nothing of the natural world. The same can be said about God, it is a hypothesis to "explain" things of the natural world, but nowadays it is no longer needed. All supernaturalism is unnecessary for science.
"unnecessary for Science"
... which says nothing about what else may exist that Science has recused itself from studying.
You have a hidden assumption that if Science can't study it, it can't exist.
Foolish mortal. :o)
Science will never have absolute certainty about anything, not even if the sun will rise tomorrow, or if the airplane will fly or fall. But it can tell you what is prudent and reasonable to believe. That is why you can travel by plane.
Science is all about reasonable beliefs, not about absolute certainties.
We finally agree about something! Progress!