Page width question

Is there any reason the ruler expands past the normal 8.5 width and margin when the screen is widen, or shrinks to less than the normal portrait size? At 100% my screen is over 12 inches wide and much more if I remove the Inspector.
I could not find anything specific that set the screen size.
I also did not know what the difference was between typewriter scrolling and fullscreen typewriter scrolling is. I am waiting on the manual to address some of these issues.
Thank you.

Because Scrivener is for making first drafts, it’s not overly focused on layout. I don’t make much use of the ruler (it’s usually hidden in my setup), but it’s mostly there for tab stops and the like. I know in the Mac version there’s a setting somewhere to set a static width for the editor which would do what you want, but I don’t know that this feature has been added to the windows version yet. Again, since I don’t want my editor to be fixed in width, I don’t make use of that feature in either environment.

What I CAN help you out with is the typewriter scrolling. Simply put, there is no real functional difference between “typewriter scrolling” and “full screen typewriter scrolling”, but one setting is for normal windowed mode, and one is for full screen mode (not maximized window, but the mode invoked with F11 or View->Enter Full Screen). You can have typewriter scrolling set up in one view, but not in the other, as you prefer.