How to get a score of 600 - 650 ?

It seems like the first thing we need to do is figure out why your real score was so much lower than what you saw on the practice tests that preceded it. How was your timing? Were you highly stressed? (Also, do you have access to your individual Quant and Verbal numbers?) It looks like you are really close to your goal, but you are not able to hit that mark consistently, so we need to see where the variation is coming in. It's quite unusual to see the kind of large swings in Quant you're experiencing--this is more common in Verbal.

Also, I have to disagree with your "First Rule of GMAT." The right answer should always be correct. If you're looking at Sentence Correction, it might not be the best way to express that particular thought, but it will be free of outright errors. In all the other areas, the answer should be 100% correct and the others should all be wrong in some clearly identifiable way. If you use your review time to identify what makes each answer choice right or wrong (in verbal) and what the most efficient path is to the right answer (in both quant and verbal), you should make steady progress.

Good luck!