Wow, the resources you mentioned are pretty extensive on the topic. That might have been as many as 400 questions that you have worked on.
Did you review those problems properly with an error log? In my opinion, it is far better to thoroughly review and track your performance on 10 problems than to rush through 100 problems just to "have done them". Make sure to ALWAYS practice with a stop watch running. Also, always review problems that you got CORRECT but that took you too long (2 minutes or more). In case you haven't already done what I suggested, there is lots of things to gain from the questions you have already done.
Apart from that, I can recommend Knewton's CR problems, but I don't know if it would make sense to participate in a course for the sole sake of getting better at only one of the 5 sections on the GMAT. In addition, I have heard that many people recommend LSAT CR, because those problems are said to be very challenging.
