This is one of the problems with the communist model. FDG wrote about this earlier in the thread: the difficulties in putting together a model to predict the necessary composition of production. However the guiding principle is that since everyone owns everything, you would not exploit it beyond what you need to take. There would be no point in building shelter that goes unused, so no one would do that. Innovation would benefit all people, and that would be the incentive to do so. The Classical idea is that with the economic problem 'solved', people could turn to focusing on progress in culture.
But arguing that everyone would need business training to manage the economy is applying a neoclassical principle to the communist model, which just doesn't work.
I don't think what Stalin and Mao did had much to do with communism as Marx described it. Stalin completely departed from the Leninist tradition in Russia, which was closer to Marx's model, and I think many of his flaws can be laid solely at his feet (mental illness or whatever other reasons there may be included). As you said, in communism, there is not meant to be any one figure who dominates history. Both Stalin and Mao broke that. Any economic model can give rise to totalitarian regimes, and to taint all of communism with the tag of Stalin and Mao does a disservice to the theory.
I don't quite understand what you're saying here. Are you referring to people who would be more swayed by socialist theory as being ones who are easily influenced? The various traditions in Marxian thought are extremely diverse, and I'm not sure they can really be homogenised like that. Though I may be misunderstanding you there.
Orwell was firmly against Soviet communism, which I think is a good argument for making it distinct from theoretical Marxist communism. 1984 and Animal Farm are good critiques of all the ways in which the USSR departed from communism. The 'centralised, top-down' model of communism that USSR practiced is so far from what Marx wrote about that it is ludicrous to hold it up as a good or valid example of communism.