I would like a clearer explanation of the +/- as well and you're right EJ is a good easy example to provide it on.  As I think about it: 
-- He was 16 / 26. 
-- 16 completions should be all positive plays.... you might count a completion as negative if he dumped off to a RB who got hit right away for a loss or if he completed a 5 yd pass on 3rd-7, so that might have happened a couple times 
-- 10 incompletions might be negative plays,... you might change it to positive for the QB if the receiver dropped it or some outstanding defensive play to break up the pass occurred, which did happen on what should have been a long TD pass to Sammy in 1Q 
-- He was only sacked once 
-- Not sure how he counts running plays.  As long as the snap isn't fumbled, or the hand off and the hand-off is clean without slowing the RB it should be a positive play 
  
Seems like EJ should be much higher on the +/-.  But generally this analysis is very helpful in understanding the team!