Science claims many things it can't prove....
Wrong. Science never claims anything as fact that can't be proven.
For instance, consider the idea of multiple universes. That is not a theory. It's hypothesis. Can't be proven at this time. Not all scientists agree with the idea either. But that doesn't mean that scientists aren't working on it, trying to find evidence to support it.
What Science does is first, identify a problem or question. Next, make a hypothesis, a guess. After that, try to prove the hypothesis through experimentation or observation. Then, analyze the data from the observations or experiments. After that, if the data supported the original hypothesis, you now have a theory.
In the english language, the word theory is bandied around a lot and often used in place of the word hypothesis. However, in Science, nothing can be called a theory until it is PROVEN.
So, in your initial comparison, remember that any time a Scientist claims something as fact he must have evidence to back it up.
Atheists are holding religious claims to the same standard as they hold scientific claims. PROVE IT.
Once a Scientific claim is proven, then it is no longer a claim, it is a theory with documented evidence to back it up.