When you list out the incorrect questions from the PT's you've done, is there a common thread to the question types you miss? You really need to dominate Must Be True, Weaken, Strengthen, & Assumption. On the last 3, dominate simple argumentation - can you quickly spot the premises, sub conclusions, & main conclusions in an argument? Once you can do that, are you able to quickly understand whether it's valid or invalid reasoning? I love the intro in Superprep for this.
Have you read through Superprep? How many times? Not just the intro, but the tests as well..
As far as going over the PT's again, I don't think there is anything wrong with that. Like you said, you've done 1200 LR problems..I'm sure you don't remember them all.