Of course after hours and hours of trying to play with the CSS and such trying to figure it out, I figured it out only a few minutes after posting this. I guess sometimes just speaking “aloud” helps!
If anyone is trying to figure out the same thing:
Turns out the code is in the header.php file is where the organization of the HTML tags are that you have to adjust.
I haven’t altered it to look exactly how I want quite yet, but I certainly got the header to span across the entire page now without being constricted to the width with the rest of the content!