You have an encyclopedic amount of questions. I'm not trying to give you the brush off, but Sheldon Browns site should answer many of your questions in a knowledgable manner. Especially regarding how to fit a bike. You may be better served referring to his highly informative site, many people on this forum do.
http://sheldonbrown.com/beginners/index.html
The question of material, steel vs carbon vs aluminum is the type of thing that tends to set off a flame war on this, or any bike forum. So you may not get a straight up answer. As you seem to have found out already.