I wouldn't go. I wouldn't even consider it. You'll get a lot more vacations, but this is your only shot at the USMLE, and you're below your target. You're terrified, yet making plans about a vacation 1 week before your exam... that doesn't quite compute.
Given how you describe yourself, I doubt you'll manage the discipline to study through the vacation week. I can imagine those 7 days being wasted, plus a couple leading up to it for preparations etc, and another couple immediately following it as you try to dust off the vacation fatigue and get back into study mode. Since a significant portion of your prep is going to be cramming, taking days off of studying at this point could really backfire.