There's no indication that Hitler ever knew anything much of Darwin at all. He never references Darwin or evolution. His ideas stemmed more from common breeding practices found in farming (which of course, was also one of Darwin's inspirations).

There's also no indication he was atheist. I'm not sure why you think he "pretended" to be Roman Catholic. Do you have references to him admitting he was merely pretending or is it merely your conjecture? Without good reason to believe otherwise, I'm inclined to take what he said at face value and accept that he was a catholic as he claimed.