Agreed - there are a few more things you can try, but if you have completed all of those sources and are still looking for improvement, the first place to look is back at those questions you've already completed. If you aren't happy with your performance yet, then you haven't learned everything you could be learning from them. And doing new questions before you've learned everything you can from the old ones... well, that's really not an efficient use of your time.
Also, I noticed that your list consists solely of practice questions. You don't list any materials that actually teach you, comprehensively, what you need to know for SC on this test. It's very difficult (and highly inefficient!) to study for the test solely by doing practice questions and reviewing the results, even if you are reviewing in the absolute best way. Or possibly you have also used materials that teach you the concepts, but you just haven't listed them?
I don't normally recommend purchasing specific MGMAT materials because I have an obvious conflict of interest, but we're talking about SC and pretty much everybody agrees that our SC Strategy Guide is the best book on the market for SC, so I'll just say so. :) I've seen the results of surveys on websites not associated with MGMAT and our SC Strategy Guide always wins the polls by a wide margin. Do ask around if you like, of course.
Now, I also mentioned that you likely aren't getting everything that you need out of your study of your practice problems. Read the below article; it describes how to study practice problems (not how to DO them... how to STUDY them).
http://www.manhattangmat.com/articles/a ... roblem.cfmThen read this article, which demonstrates how to analyze one specific SC question:
http://www.manhattangmat.com/articles/GMATprep-SC.cfmIf you haven't been doing that kind of analysis on the problems you already completed, you need to go back to them and really study them - most of your learning comes from your analysis after trying the problem in the first place.
You may also find this article valuable:
http://www.beatthegmat.com/mba/2010/06/ ... on-problem