I would agree with most of your comments on the defense, but the turnovers I'm willing to cut a little more slack. We're middle of the pack in interceptions (and Clements missed a golden opportunity for another one on Sunday) and fumble recoveries involve a lot of luck IMO.
The 3rd down conversions and seeming inability to stop teams when it counts are very frustrating though. It's not that I can even say the defense is "bad" because they've shown themselves capable of shutting teams down for long stretches. Lack of focus or bad defensive philosophy on long downs?