Inconsistent Results - Constant Fluctuations - Any Advice?

First off, congrats on your score. I know you expect more from yourself, but regardless your score gives you a chance anywhere in the world. If you wan't to improve your chance, it won't be hard to do--but it will be tedious.

1. Make a binder of every question you got wrong on your practice tests.
2. Using that binder, go through it EVERY day. Ask other people how they did them, find videos on youtube, use this forum. You get the idea.
3. Once you can consistently CORRECTLY answer each question UNDER TWO MINUTES, and most importantly CAN EXPLAIN WHY THE ANSWER IS CORRECT, you are good to go.
4. I also did math and verbal questions throughout the day. Five minutes here, five minutes there. It helps you be mentally agile at all times. Have a test in the AM? You've done this in the AM. Have a test in the PM? You've done it in the PM. You're ready for whatever.
5. And lastly, what I found most important--Do at least one to two hours a night. When you're dead tired. Why? Because ultimately what may cause that score to drop is fatigue--fatigue from anxiety the night before, fatigue from sheer nerves, fatigue from the annoying processes at the testing center, fatigue from staring at a screen so long. You need to build endurance.

You obviously have the brains, now kick some ass.