I understand. The best way to get strong is to face and overcome the weaknesses. Here are a few things that I would suggest -
Math -
1. Start from the scratch. With your current experience in doing the challenges, you will have a fairly good idea on what your weak area is - among Algebra, Geometry, Probability, Arithmetic, Data Suff. or Number properties...
Identify those areas and take out the basic Math books and strengthen the fundamentals. Any strong tree has strong roots. Strengthen the base or fundamentals, you will see the difference.
2. I know you have too many study materials now. Don't let that be a hindrance, instead use them effectively. Remember you may not have time to get your hand on each of those. Once you are fairly comfortable with the concepts. Take out the
OG and start solving problems from the beginning. Keep an
error log. As soon as you are done with a set of questions, check the errors, go back to the books or work to correct them and make sure you don't go wrong in the same area again.
3. I believe Kaplan is also good for Math study. I don't know, maybe someone else will be able to provide you with more info.
4. Once you are comfortable in Math, try to be involved in participating in the Math Forum.
Verbal -
1. Again, it is more of getting practice. I found the Kaplan review helpful. Read how to approach the questions (esp. RC) and then start working again each of those sections with
OG.
2. Better if you first try stuff like
OG and Kaplan that explain the answers before you move on to 1000 SC and others.
Again, GMAT doesn't measure your intelligene. Sure, some are geniuses who score 700+ on any day. But 99% others are normal. All it takes is a thorough introspection, hard work and above all discipline. Decide on the test when you think you will be ready. When you feel confident, you can shake up GMAT!