Hi zmzm,
With a Test Date on May 16th, you have a little more than 3 weeks of study time, which is probably NOT enough time for you to improve to a 650+. There are some other issues that will take time to "fix", so you might need to consider pushing back your Test Date and putting in some additional study time.
You have NOT taken any FULL CATs yet, so we don't know what your actual abilities are. The Full GMAT is a very specific 'event' that you CAN train for, but you haven't yet. From now on, you really must take the ENTIRE CAT each time (including the Essay and IR sections). You will also want to take your CATs in a way that matches Test Day (same time of day and day of the week if possible, take it away from your home in a test-like setting, etc.).
1) What resources have you been using during your studies?
2) You mentioned a Test in June. Is that something you are planning for (have you actually scheduled the Test?)?
3) When are you planning to apply to Business School?
GMAT assassins aren't born, they're made,
Rich