I am actually thinking of justing putting everything at default to be honest with you. I have no idea if 0 Speed Threshold is making guys get off blocks quicker but I felt like I saw a huge number of sacks when i tried it at 50 to.
Even with the sack issues most of my games are competitive. I never really have guaranteed wins, the Bears have my number for some reason. The bottom line for me is that the game is still fun. I just have to be able to not worry about sacks and messed up stats so much and for the most part I have done that.
In my first season i was messing with sliders trying to many different things and it got annoying. I just wanted to play the game without worrying about that stuff and I have done that in season 2.
In answer too your second question I notice it mostly when the Qb just stands in the pocket and gets blown up. I have had games where I am getting lit up in the secondary so I start blitzing constantly and I still don't get a ton of sacks. I agree with someone else who said pocket passers are worse in regards to the sack issue.
I wish there was some clarity in regards to what causes it but I don't spend time looking at other teams confidence before I get big sack games or the ratings. I know most of my guys confidence is pretty high. I think it's too easy to get sky high confidence numbers but I don't know how much they affect the gameplay and i haven't heard the devs say how much it really does other than raising some ratings a few points.
My main wish is that they could figure out how to have the Qb throw the ball away a little bit more. Make some more of these sacks into some of the errant throws and it would clean up the issue with QB % as well.
Bottom line the game is still fun so i will keep playing it through football season and I would still consider getting the new one next year depending on what they bring to the table. I don't buy the game at release anyway so i can wait to hear things, good or bad.