I clearly remember how stressful it feels right before the MCAT. I'm sure you realize that no one out there can really give you a very definitive answer about your chances, because while numbers go a long way, they are not your entire application. That being said, I guess the best question to ask yourself is how do you really feel about your practice scores -- do you feel that you haven't studied as much as you should have, or that there was something that has been getting in the way of you fully concentrating on the MCAT? If you get these exact same scores on test day, would you take the test again? If this is the case and you honestly believe that you could score better with more time, then my advice would be to wait and take the MCAT in April. This is just based purely on my own experience -- I was all set to take the April 1999 MCAT, but I kept getting 28s or 29s on every single practice test. It was 4 days before the MCAT and I was freaking out. My scores were not improving in the least. Also, I knew that I had not put in nearly as much time as I could/should have, due to certain outside factors. Essentially, I really felt I could do better with more time. I decided not to take the MCAT 3 days before the test day, and instead I took it the following April, and did MUCH better, and I felt better about the whole process -- the first time around, I couldn't even sleep the week before the MCAT because I was so anxious! I wasn't thrilled about waiting an extra year, but I really think it paid off because it made me a better, stronger applicant this first time around.
If you are committed to taking the exam this weekend, devote your time to practice tests, and then reviewing the answers to missed questions. To keep your energy up, try to bring some sweet fruit with you, or Power Bars, Balance Bars, etc. Everyone has their own tried and true remedies, but this worked well for me because the sugar gave me a little extra boost, but it wasn't too much food at the same time.
Whatever you decide, feel confident about your decision. Good luck.