Hi vadey23,
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 home, taking them at different times of day, 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 3.5 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.
In addition, the process of taking (and reviewing) a CAT requires a significant amount of energy and effort - and takes time to 'recover' from. This is one of the reasons why you typically shouldn't take more than 1 CAT per week - and your last CAT should be taken about 1 week before Test Day. By taking a CAT in the last couple of days right before your Official GMAT, there's a reasonable chance that you experienced some 'burn out' on Test Day. The extra study time during that last week, going to bed later and the lack of sleep that you got the night before the Exam likely all contributed to that burn out. You described how your stomach was 'growling' during the Test; do you eat breakfast every day? Skipping breakfast is a big mistake - the brain and body need fuel to perform at a high level, and if you're not giving yourself that fuel, then your Test Day performance will suffer.
Thankfully, these are all relatively easy issues to fix - now that you've taken the Official GMAT, you know the EXACT details of what happens on Test Day, so you can better train to mimic those details during your CATs. In addition, you do not have to correctly answer ANY questions that you think are too hard or too weird (so getting comfortable with the idea that it's okay to quickly 'dump' a few tough questions should help you with your overall pacing. That all having been said, raising a 370 to a 500+ will likely take at least 2 months of additional study time - and you'll have to work to hone specific skills in BOTH the Quant and Verbal sections.
1) You mentioned having to travel a lot during the summer. Are there going to be periods of time (days or even weeks) in which you won't be able to study at all? If so, when will those dates be?
GMAT assassins aren't born, they're made,
Rich