Hi Mourad,
Test Day is a rather specific 'event' - the details are specific and they matter, so you have to train as best as you can for all of them. The more realistic you can make your CATs, the more likely the score results are to be accurate. The more you deviate, the more "inflated" your practice scores can become - and that's what happened here. By skipping sections, taking the CATs at different times (from when you took the Official GMAT), pausing the CATs, etc., you weren't properly training for the FULL GMAT 'experience.'
Test Day involves a variety of really specific steps and parameters (including steps before the Test even begins - such as leaving your home, traveling, etc.). Every factor matters, including the psychological ones. When you sit down on Test Day, you KNOW that you're going to be in the Computer Lab for about 4 hours - but if you're just taking individual sections (or taking a CAT without the Essay and IR sections), then you KNOW that you'll be done in 1-2 hours. The attitude and energy that you use during practice will NOT be a match for what you'll need on Test Day, so it's not a proper way to practice.
While it's certainly possible that you had a bit of a 'bad day', your current 'ability level' probably isn't much higher than the mid-500s. Raising a 550 to a 660+ will likely take at least another 2 months of consistent, guided study - and you'll have to make significant improvements to how you handle BOTH the Quant and Verbal sections. With just 2 weeks of study time left before the end of February, that type of score improvement is likely too difficult to be considered realistic, so you might want to consider shifting your application plans.
1) What are the next set of application deadline(s) after March 1st for the Schools that you're interested in?
GMAT assassins aren't born, they're made,
Rich