I was thinking that the dreamer would not be hurt by their own nightmare.  As for the control thing I think that would be tricky since the nightmares would have their own personalities.  However that could be something that maybe one in every 1000 people can do and that would make it rare enough that not many people had heard of it.  They would have a different ability because of a different gene mutation as well.  And then yeah they could then in fact make their nightmares do their will.  But if the nightmares ever got out of their control I don't think they would like it much since if I was a nightmare the first thing I would do was kill my controller after killing anyone that they loved or had spared before their eyes.  What do you think?