I went from an 1890 to a 2010 in...6 months, but I didn't really study for CR or W- just math! And it only went up 50 points to a 580, so I'm retaking again! And I have less than a week to study. ):
But you can do it!
Instead of trying to cram a bunch of vocab words into your head, try learning roots instead. It's helped me a TON. Also, when you get a word you don't know, think of words it is similar to. For example, I had the word "abstemious," and I didn't know what it meant, but I knew that "abstain" and "abstinence" meant keeping away from things, so I knew then that abstemious was not the right choice for the question. And I got it right!
If you don't have time to go over all the math concepts, I suggest you look up tricks and shortcuts in the math section, because they're definitely there. I used the SAT Math Bible, and it was extremely helpful for me.
As for writing, if you made a 750 on the practice test, then you can do it on the real test! Just don't be nervous!