Stuck at 35 (verbal score)

Hi lee07,
I am in the same boat. Took 4 mgmat CATs and scored 35V in each. I am non-native as well.
Concentration is crucial and the best way to impove it is to do as much tests as you can.
You defenitely have to do both sections but stay close to OG and don't use a lot of ambiguous sources. If you already exhausted (and I suppose you did) all og materials, read all explanations for cr, not only for those you did wrong but for others as well. It will help you to follow the logic of authors and realize how it actually works. Having done bunch of problems from unreliable sources I started to notice what questions are of good quality and what are not. OG (13,2) and mgmat tests (cr questions) are more than enough for you to do the best on the actual test. Generally, CR is the next section (after SC) that you may improve in short time.
Things are more difficult with RC. It requires a lot of time, more than one can believe. I think you need to observe what topics you are more comfortable with (say history) and what are the dark side for you (science for example). Then you will concentrate on your weak area. The same thing is with types of questions. My problem is 'inference' type, so I work on it actively.
The fact that you do more mistakes on easy problems means that you try to find a trap where there isn't one. You just start to be suspicious, but most questions are not too intricate as we would like them to see.
Good luck with your perfomance.