About the first. I'm not very interested in the more technical aspects of the ip, and can't really help.
About the second, however, we have not one, but two precedents Kyle Katarn (Jedi Knight series of video games, some comics and novels) uses both dark and light sided powers, teaching that the powers themselves aren't inherently good nor evil, but how you use them. He teaches this to his padawan, Jaden Korr (Jedi Academy video game, some novels, most notably Crosscurrent which deals with him coming to terms with his former master's teaching and his apparent slippage to the Dark Side due to prolonged use of the Force Lightning), who then masters the same techniques. Both are stated to be somewhat unique, but you did ask for a precedent, and there they are
(Excuse my probably not-so-stellar english, it's rather late and I should be in bed instead of lurking the forums )