But they don't believe in evolution, they believe in theistic evolution, that is, evolution guided by god, which is not really evolution. One of the fundamental aspects of evolution is that it does not require a guider, just chemistry, statistics, and time.
No, they don't (well, some of them do, I can't really speak for all of them). God doesn't have to guide evolution: why would he? He's an omnipotent omniscient being in Catholic theology: he is completely capable of creating the universe with a set of physical laws that will result in evolution following the path he wants it to without intervening directly in it later.
It sounds like you are describing a god whose existence is indistinguishable from it's non-existense. How would you ever tell if that god exists? Why should anyone believe in it if you can't tell?
Scientifically, yes: the universe with a god is indistinguishable from one without one (well, aside from the fact that the universe does actually exist, but that's a long argument I won't engage in here). That makes sense: science deals with the natural, not the supernatural. In fact, even if God did regularly directly intervene in the physical world, there still would be no scientific proof he exists: science would attribute it either as a natural process if it happened regularly (even if it didn't fully understand why) just as it does with all regular processes we see in the world, or a statistical anomaly also caused by natural processes (albeit unknown ones) if it happened irregularly. That's because that is all science can do: to ask it to talk about supernatural beings is like asking your eyes what noise tastes like. That is simply not how it works. Science looks for natural processes governing nature. It literally cannot see supernatural events. All it would say is "some effect we cannot yet fully explain."