1. Sensei Wu got the lesson book back in the episode Lloyd stole it, I don't think it will be appearing again I think it was just something the writers came up with to have Lloyd steal to show how he is still having trouble adjusting to being good and not evil anymore. 2. My guess it will be some sort of virus/infection thing that infects him and turns him evil like some kind of mind controlling nano-virus. 3. I believe that he can produce less electricity than that like a little zap or something instead of him just creating a giant blast of tons of watts. 4. I think Dareth should come back, though I doubt the ninja would be foolish enough to leave to army in Dareth's control that would be like in Star Wars they gave Jar Jar the controls for the Trade Federation droid army. Giving the command of an entire army. So I believe they probably destroyed it or at least hid it somewhere safe.