You scores aren't bad~
I posted a similar thread on the GMAT forum, but more specifically on SC (I've been doing <50% on that section in my
MGMAT CAT exams, with 85%+ on the CR and RC).
With CR and RC, the
MGMAT book really helped me. For RC I've found that spending the time to jot down 2-3 notes/lines per paragraph helps frame my thoughts better. The "general purpose" or "intent" questions on the RC part were difficult for me before, but now after I do my mini paraphrase, I write a little statement at the end about what the passage tried to show. Generally, one of the answer choices will match up fairly well with that summary.
CR still sometimes confuses me, but trying to "see" the conclusions and assumptions breaks those questions down in a more analytical manner.