Score isn't improving

It's very interesting. The problem as you describe it is much more related to your attention skills than it is to any problem with cognition or test-taking abilities. It may be that Magoosh will help you get a bit faster on the 700-800 Quant questions and give you a bit more clarity with those final two RC answer choices. The juggernaut, though, is something that really no GMAT test prep source can give you: greater command of your attention and focus.

First of all, I would say, read these three blogs:
a) https://magoosh.com/gmat/2012/overcome-g ... y-breathe/
b) https://magoosh.com/gmat/2012/beating-gmat-stress/
c) https://magoosh.com/gmat/2012/the-gmat-b ... g-picture/

OK, so you have a month to build your attention and focus skills so that you can perform at a higher level on the GMAT. It can be done, if you are up to the challenge. (1) No TV or videos games in the next month. You need to get your mind away from artificial "attention-magnets" so you can develop more conscious control. (2) Every waking moment of every day you should be breathing slowly and deeply, regardless of whatever else you may do (of course, you should get physical exercise every day, and during vigorous exercise, just breath the way your body needs --- that's the only exception to the "breathe slowly" advice). (3) Eat healthy --- avoid everything with "high fructose corn syrup." Avoid caffeine and energy drinks. Avoid alcohol and drugs. Drink 8+ glasses of water a day. You need to cleanse the brain's biochemistry. (4) Get adequate sleep, 8 hours a night every night. (5) Practice noticing details. Start in the most familiar environments: home, office, commute to work, friend's house, etc. Each day, or each time there, force yourself to notice one new thing you had never noticed before. (6) You might even skim an article or book about mindfulness (Jon Kabat-Zinn is one of the world's leading authorities on this.) ------- This is something of a "austerity diet" for the mind, because you have only a month to get to Jedi level in skills that are woefully underdeveloped in our post-modern electronic culture. Virtually everything about modern culture mitigates against the development of these skills.

If you could maintain these restrictions consistently for a month, they would develop your ability to focus. If you could live your whole life this way, it would enable you to command your attention & focus, giving you a decided edge in the business world and making you that much more effective in almost every other endeavor in your life. It's the edge that anyone could develop but which, in practice, almost nobody does in this day and age.

I know this is not the answer for which you were looking --- you just wanted me to tell you, work through one more GMAT prep book. That's what most people do. If you want the results that most people get, do what most people do. If you want extraordinary results, you must take extraordinary steps. Yes, do some more GMAT prep also ---- frankly, I think Magoosh would help you much more than the options you listed --- but whichever you pick, in a way that alone is just more of the same. If you want to break through the ceiling you are currently experiencing, that will require some radical changes, not just in how you think, but more in how you are.

That's my advice. Please let me know if you have any questions, or if there is anything which you would like me to clarify. Best of luck to you.

Mike