Pretz,
First I just want to say, you can do this! You're approaching this experience well and demonstrating commitment to the task at hand. With that said, it seems like you have done a lot to practice new material, but how often do you review the problems you have already done? Sure you're getting plenty of questions correct, but are you always able to articulate why? Check yourself for the silly mistakes, and places where there are gaps in fundamental knowledge. You may know the fundamentals, but are you able to apply them in the heat of the moment? I struggle with that sometimes. Essentially, review those error logs and identify potential weaknesses. If you see where you went wrong in a question, make a flashcard reminding you of the particular formula/concept you missed.
Secondly, I'm sensing some mental fatigue. I'm not sure 5 hours a day and 10 hours a day are going to do you any good if it only tires you out. Furthermore, you need to give your brain a chance to solidify the material you are learning practicing. I used to teach High School drumline. If I didn't give the kids a chance to let new material soak in, they would go brain dead after practicing too many hours straight. You would be amazed what brief intentional breaks can do to solidify concepts. I'm not saying you take a week off, or even a day, but giving your self a mix of heavy study days and lighter review days may be benefitial.
Lastly, I supposed I would suggest that you not focus on a 750, not because you cannot acheive it, but because it will more beneficial for you to simply focus on one question at a time, mastering every concept for each question you face. Otherwise, you may put too much pressure on yourself to perform.
You can do this, and do it well!
I hope my post was helpful.
~David

Thank you so much. This makes more sense. Yes, I was not reviewing the questions as frequently as required than I am rushing to finish more and more problems to track the patterns of the kind of questions that may come in the test.