Hi Mechmeera,
From what you describe, it's not clear what the MOST important thing is. I'm going to assume that you want a high GMAT score so that you can comfortably apply to your top-choice School(s). In this way, everything comes down to your GMAT score - and you have to be ready to adapt the other parts of your 'plan' to fit THAT goal.
If you don't have a competitive GMAT score, then the immediate Business School admissions deadlines will NOT matter. You CAN always apply for a later Round though. If you take the GMAT in 20 days (as scheduled) and do not hit your score goals, then you'll have to pay another $250 to take the GMAT again (considerably MORE than the $50 rescheduling fee).
I bring all of this up because (assuming your CAT scores are accurate), your goal is 110+ points away and you have less than 3 weeks until your scheduled Test Date. Thus, it's unlikely that you'll hit your score goal in that time... but it could be that you don't *need* a 750+ score (you just *want* it). There's no harm in continuing on as you've planned - use your resources, continue to study, take a couple of additional CATs and then take the Official GMAT. If you score in the mid-600s to high-600s, what would you choose to do then?
GMAT assassins aren't born, they're made,
Rich