Lets not forget that stalin was allied with Hitler early on, and they only came to be at odds because Hitler stupidly invaded Russia. The "communists" are not some sort of default good guys back then, or now. They are as morally bankrupt and inhumane as the capitalists, just poorer.
I don't think that's a particularly good idea. Hitler was charismatic, but there's a pretty strong impression among historians that he made a lot of dumb decisions that ultimately helped the Nazis lose. If you take out the bungler after they're already in power, he gets replaced by a more competent leader who won't make as many mistakes.
Yes. Let's never do anything to improve our situation because it might actually deteriorate. With that kind of mindset, you better never leave your bed.
Seems to be that the most effective thing for the Allied resistance to have done would've been to target the competent people around Hitler, who were not only potentially more dangerous, but also less well-protected by the SS. Senior advisors (especially "true believers" and policy wonks), yes-men pushing his agenda through the legislature, partisan judges, etc.