You can't identify something as an overconfidence error until you know you've missed it. An overconfidence error is a question that you didn't mark for BR but missed. So other than scoring the test, there's no other way to identify OC errors for review.
PTs from LSAC can also have spelling errors, it happens sometimes. Often when we have one with a spelling error and you do not, it means we have the original print and you have the updated print.
As a TA, I used a Scantron machine a handful of times. A small tear on the side likely won't affect how your answer sheet is graded.
If you're absolutely paranoid, just have them manually grade it, as @"Cant Get Right" suggested.
Hey i accidentally tore my December 2016 scantron a little bit and there was no issue at all. I received my score on the same day as everyone else (in an early wave, too!). You'll be fine.