Since you are from Illinois, we'll need to see your FOID before discussing guns with you.
Sorry- could not resist the cheap shot!
In a nutshell, consistency is the key- you want your cheek meeting the same spot on the stock each time, so your view through the scope is identical- each time.
Using a scope is actually easier than iron sights- since you have fewer points to focus on. You have brought up a lot of questions in one or two, more than can be briefly answered.
The one issue that pops up is one eye or two? I shoot with both eyes open- focusing on the scope- some folks have a hard time learning to do that.
Rather than try to instuct at long distance, not having a clue what you are shooting, and your experience level, I am going to suggest you find an Project Appleseed shoot near you, and get into that. Link for you- Project Appleseed Home