It sounds like you're doing everything you can at the moment. In all honesty, as frustrating as the test can be/has been for you, posting about how much it stinks on here probably isn't going to do much other than amp you up even more. Given that it sounds like you're sitting for the exam in 2 days, being worked up probably isn't going to do you any good.
If you've been hitting over 300 on practice exams but got below that on the "real deal," then you at least know where things stand in terms of what you can accomplish, although of course there are a variety of other factors that come into play on the actual test day. If things go well this time, awesome. If not, maybe start to really see if you can identify specific things that you feel detracted from your performance, and whether they're in your control (e.g., got flustered and ran out of time before finishing; the room was freezing and you didn't happen to think to bring a sweater) or not (e.g., the computer setup wasn't what you were used to).
As for vocab, I personally found that memorizing a slew of new words (probably around 600-700 or so) helped, but I'm also fortunate in that the English/verbal portions of these types of tests tend to go fairly smoothly for me. Standardized math testing has always been my weakness, so I made sure to brush up on as many forumulae as possible...and even with all that, I think I only hit low-to-mid-600's. In my case, if I had needed to take the exam again, I definitely would've looked into recognizing and learning to efficiently respond to the types of questions themselves, as that's an entire strategy all its own. You've probably already done this yourself, but it's the only personal insight I can offer into things that would've helped my own performance.