OP, I understand and personally commend you for taking the time, with others, to learn about American football. Like a lot of sports, which are win/loss based, it's easy to focus on the macro aspects of a given game. It's the devil in the details that can be hard, but are what answer the "why" things are happening. It comes a bit easier if you've actually played the game, even in talking with folks who've grown up here (but haven't been in the game). If you want a real challenge, try American baseball, which I've played the most, that'll really hurt the mind.
I wont offer a whole lot of advice, so I'll focus on one or two. First, the SEC is a line of scrimmage game, to a great deal. Our previous coach (CBJ), IMO, decided that he wanted offensive linemen that were lighter and faster.......he got lighter, but not much faster (because at this level, he didn't understand, you could actually get both). In your world(?), it's like a rugby coach saying he wants mostly speed, but at the cost of any size in the front, aka weight (try that **** with the All-Blacks). And he recruited/played like that for 5 years. He did okay for a year or so, but never won anything of significance. Because of that philosophy he regularly got killed by the Alabama's, Florida's and Georgia's of the world..... NOT ..... understanding that is who you HAVE TO beat. Doing 8-4, and losing to AL, GA and FL consistently means you've got your wires crossed.....or...in his case, he didn't get it at all.
Lastly..... when you've recruited at the LOS, for 5 years, fast and light, it takes at least 2-1/2 to 3 years .... if not 5 to overcome it. Just like it would be in rugby, i.e. You do NOT get to recruit big boys on a whim, it takes years to develop them. It's actually early (complimentary) to say we have seen improvement in the OL this year. The OL directly impacts a team's ability to let the QB pass...and the RB run...fundamental aspects of this game......in the SEC. Screw up in the OL and you screw up your passing and running game. They are not independent, they are synonymous. I'd go into the DL but generally the same principles apply, just in a different way.
I hope this in some way is helpful.