I would think yes to both, IMO. I think Jedi Masters tend to warn their padawans very much against anything remotely connected to the Dark Side because of how seductive and easy it is. Even if you tap into it even once, only the strongest of Jedi might resist the temptation to use it ever again, especially during a fight.Force-lightning should be mentioned as a mostly Sith ability. Jedi presumably can do it too, but don't as it may be viewed as a Dark Side power, IMO.
Oh right, I forgot about that one. Does using dark side powers make a Jedi more vulnerable to the dark side? How about just committing evil acts in general?