For league-wide rating level distribution, please see my thread/study on the the subject. Be warned, it's a rather long read though. However, I can tell you right here is that the average for every rating category is different.
League-wide rating level study:
http://www.ootpdevelopments.com/boar...threadid=64539
I also have two reference links on rating/stat conversion (for default/modern league total setting) in that very same thread. The links can be found in the conclusion section of the study.
As for what rating reallys means, this has been covered in the forum from time to time. I can tell you as a brief describtion. But for more detailed explanations, please search the thread since I only have a vague memory of what rating means.
Stuff is the ability to strike out batters.
Movement is the ability to prevent homeruns, not really the ability to force groudballs. The ability of forcing groundballs is covered in "Groundball%" in the player "General Info" section. The 'game effect' of groundball% is still in debate as far as I can remeber