I wouldn't agree that your potential score depends on your intellectual ability at all. I bombed the SAT on my first take (second one was snowed out), but I graduated in the top 2% in my high school and #1 in my major in college. Not trying to toot my own horn here, but my score totally didn't correlate to my abilities. My first GMAT wasn't a shining success either, although I was sick and did score a full 100 points less than in my practice tests!!
To the original poster (OP), you have quite a slew of practice materials, but I'm kind of surprised you opted for so many workbooks on the individual sections rather than an overall review guide that also has practice tests. I do agree that you don't need to prep much to get a 500, but you should at least take a few full, timed practice tests on the computer as part of your prep. Otherwise you're going to get a nasty surprise on test day!
Download the free official tests from
https://www.mba.com (they're called GMATPrep), and if you have time, also do the Princeton Review tests that come in their book, Cracking the GMAT (well, the tests are online but you need the DVD that comes with the book to take them).
Kaplan should be helpful for your quant prep but stick with official materials and Princeton Review for verbal. Since you aren't aiming for a high score, your older OG should be sufficient. Quant's gotten a lot harder but if you're targeting a high quant score the 10th edition is ok. Otherwise I'd say get the 11th.
Hope this helps!