Personally, I think the rebuilding of the Jedi order in the face of a galaxy-wide threat is the way to go. The only Jedi left is Luke, so where is the sith supposed to come from?
From what I understand, Luke is the only Jedi or Sith left at the end of Return. That is balance IMO. In episode one, Yoda kept harping on and on about Anakin being the one who would ultimately be the one to bring balance to the Force. He was right, just not in the way he thought.
I've never thought so. I took a good screenplay class once and that was never the problem. Giving the characters something to do was. Plus, actors ad-lib a lot anyway.
Come up with your plot, then characters, then dialogue. When you write, you have to picture what will look and sound best on screen rather than what reads best on paper.
There are some sites out there that have copies of scripts that made it to production. I suggest checking some of them out and even keeping one open while you type to reference it when you aren't sure what to do with your script. For me, I peek at one just to make sure I'm fine from an organization aspect.