PS questions and question about the gmat books !

Hi everyone!
First of all, I would like to say that it's my first post ont he website! However I am registered to the gmatclub for 3 or 4 months now. Oh and also, I am french (that might explain some english mistake I could do ....)

I have 2 questions:

1) gmat quantitative review 2nd edition question 156 (PS)

"If \(4< \frac{(7-x)}{3}\), which of the following must be true?

I. 5 < x
II. |x+3| > 2
III. -(x+5) >0"

Answer :
First of all let's simplify the expression. We obtain : x < -5

I. Obvious that it is not true.
III. Obivous that it is true

II. For me |x + 3| > 2 means that x is in [ -inf; -5] U [-1; +inf]. i.e we don't only have x < -5 which would mean that it is not true (I think).
But as you can see it coming, the answer is that the statement is TRUE. WHY ?????????

I hope I made myself as clear as possible on this question....

2) As I am very studuous, I am working with the three gmat books and the gmatclub tests.
For all the questions of the "gmat quantitative 2nd edition" I got 272/300, i.e. 90.6% (and I am working on a train) which does not seem that bad.
However for the gmatclub test, I am often less than 50% (percentile) and around 9/10 mistakes. My best score is 75%. So as soon as I start doing the gmatclub tests I am feeling really bad, like if I was hopeless....

Is this range normal? Am I hopeless? Could you give me some advice? I am trying to follow some guide posted on the gmat forum as hard as possible but even if I can see some improvements I just reduce my mistakes from 12 to 8 when.

Thank you in advance if you can answer my questions,

Alex