Hi Olly,
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, pausing the Exams, 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 also have to TRAVEL a significant distance on Test Day (which you did), then you also have to account for THAT time and effort. The details about how you took your CATs during your practice were NOT a match for what you faced on Test Day. All of the 'differences' involved in how you took your CATs could explain why your Scores dropped - you weren't properly prepared for THAT full day, so your Scores fluctuated.
Beyond all of those issues, the other factors that you described about the last 3 days before your Exam also define some areas that impacted your performance. 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 right before your Official GMAT, there's a reasonable chance that you experienced some 'burn out' on Test Day. Long travel days often tire people out - so we can't ignore that potential impact on you either. In addition, a poor night's sleep would hurt most Test Takers - and not knowing exactly where the Test Center was probably added some stress to an already challenging situation.
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. That having been said, raising a 560 to a 700+ will likely take at least another 3 months of consistent, guided study - and you'll have to make significant improvements to how you handle BOTH the Quant and Verbal sections.
1) What Schools are you planning to apply to?
2) Going forward, how many hours do you think you can consistently study each week?
GMAT assassins aren't born, they're made,
Rich