Well I prepared for 2 months too and got a fairly good score. You may wanna go through my debrief and see if you can get some insights.

Could be a variety of factors including the getting most experimental questions correct theory that you have proposed but since you are targeting a reasonable score of 650, I think you MUST retake the GMAT. Start working on your weakenesses and you should be good to go in a month

You can probably start doing the preliminary work form now itself- keep aside half an hour per day and you will see that you'll be quite prepared

There are two things here. Firstly the books you use(read my debrief for the ones I used for SC and CR) and the way you use those books. Your focus should not be on completing the books fast but rather on understanding the stuff well and understanding the application of concepts

15 on Verbal is too less I think and means that you are concepts(and their application) is not strong enough yet. You may need to change the books you're using or the way you are studying to able to leapfrog to a decent score on Verbal.

Good advice by GMATKolaveri. I think you need to first see what are the areas you need to focus on -say Verbal or Quant and then you should ask yourself what sub areas do you need to focus on in Verbal-SC,CR and RC and then address each area accordingly.

Good suggestion by gauravdangi. 20 hours per week is a good amount of time to dedicate to the GMAT. Beyond that would be a stretch I think and you will feel exhausted after a couple of weeks if you study too much

Seems like you have exhausted most of the material. 1. Yes, SC is not only about rules but understanding their application. You may want to go through the Manhattan SC again else you will find SC Grail 3rd edition quite helpful. 3. AFAIK, initial questions matter but not very much. You can always bo...