1) To the difference in the defense - I imagine if you look at 3rd down conversion rate, there is your answer. Our offense failed to extend drives and our defense failed to get off the field. We're a bend but don't break type of scheme and the more we're on the field.
2) Pass rush is also reliant on an ability to cover for 3 seconds roughly. If you can't cover, you can't get pressure. So in general dropping 8 in theory gives you a chance to give your rushers a chance to get there. An experienced QB who gets rid of the ball fast largely renders a pass rush moot. So you have to be able to take away the quick and intermediate game then get pressure, unless you are going to commit to blitzing but that's not our concept. Our concept is largely keep the ball in front of us, rally and make the tackle.
Also, since we typically don't have a ton of track stars - rushing 3 allows us to get another skilled player on the field to in theory get us quicker to the ball when it is thrown on the perimeter or down field.
Michigan has 2 NFL - possibly high NFL edge rushers. Both of those kids are monsters. But even with that Ohio State threw for 394. You aren't sacking people all the time.
3) As for the OL - for one, UNI's defensive line is arguably better than some FBS defensive lines. Has been since guys like Bryce Paup where there. It needs to gel yes, but its not just on them. Id say we need to have a more clear identify of who we are and how we are going to go about doing it than we seem to have in September. It seems to take us 3-4 games to figure out exactly who we are in terms of a play calling perspective