Hi thesouthpaw,
The scoring Algorithm on the Official GMAT is far more complex than most people realize - and it factors in far more than the percentage of questions that you get correct. As such, that statistic isn't nearly as meaningful as you might think it is (or might want it to be). When it comes to picking up points, you have to look at all of the questions that you get wrong but COULD/SHOULD have gotten correct. In the Quant section, you already seem to recognize when you made a little mistake on a question. In the Verbal section, you should look for questions that you 'narrowed down to 2 choices, but still got wrong' - in theory, you were really close to getting the correct answer, but you still missed something vital in the prompt.
Taking FULL-LENGTH CATs (including the Essay and IR sections) at regular intervals is a really important part of training to face the Official GMAT. As such, you should plan to take one every 1-2 weeks as you continue to study.
GMAT assassins aren't born, they're made,
Rich