Hi Dodododo,
There are a number of different issues to discuss:
First, raising a 580 to the point that you can consistently score 700+ will likely require 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. Considering that your 4 Official Scores are so similar, it's likely that you have developed some 'bad habits' during your prior studies that will take time to fix (and replace with new 'good habits'). By extension, you might need even more study time to get to your Goal Score. Thankfully, the GMAT is a consistent, predictable Exam, so you CAN train to score at a higher level. However, the goal to make all of those improvements in about 30 days might be too difficult to be considered realistic.
Second, GMAC's testing rules 'limit' each Test Taker to no more than 5 attempts in any 12-month period. Given your 4 prior Test Dates, IF you were to take the GMAT in May and not earn a Score that makes you happy, then you will have hit your 5 attempt limit (and you would have to wait until you have passed the one-year anniversary of your first Score date - from last June - before you could retest again). Thus, "rushing in" to retest in May would impact your overall schedule (re: when you could retest again).
Third, based on the information that you've provided about your 4 Official Scores, you'll need to work on both your Quant and Verbal skills. Unfortunately, your plan to study 5-7 hours a day is likely far too much study (and it sounds as if you are confusing "quantity" of study with "quality" of study). By studying in that way, you will greatly increase your risk of "burn out" before Test Day (and that is something that we want to avoid).
At this point, you have to decide what is MORE important: taking the GMAT in May OR hitting your Goal Score? If you think that you "need" a GMAT Score in the high-600s or 700s, then you need to give yourself more time than you have allotted and commit to at least 2 months of consistent, guided study.
GMAT assassins aren't born, they're made,
Rich