Hi Iskov,
There's a big difference between performing well on small quizzes or random sets of practice questions and performing at a high level on a FULL CAT taken under realistic conditions. As such, it's possible that the way that you've been studying is actually keeping you from scoring higher on the Full Test; since you do well on small practice sets, you think that you have developed the necessary skills to do well on Test Day. You probably know the content reasonably well, but your Tactics and organization need a lot of work - and you need to train to make good decisions under 'higher-pressure' situations (re: when the clock is winding down on Test Day).
With your current Test Date, you have about 1.5 weeks remaining. Based on everything that you've described, I think that you have developed a number of 'bad habits' that will take time to fix (and replace with new 'good habits') - and that training will take far more than the time that you have allotted. At this point, I think that you should consider reaching out to the School that you're interested in and ask to delay your application; it certainly seems as though the School's representatives are interested in you, so they might agree to the request.
If you have the option, then I would suggest pushing back your Test Date. If you still plan to take the Exam on July 6th, then you should note that to hit your Goal Score you do NOT need to correctly answer ANY questions that are too hard or too weird - so the smartest move would be to quickly 'dump' a few questions and use that extra time to do more work (and double-check it when appropriate) on everything else.
GMAT assassins aren't born, they're made,
Rich