640 (48 Q, 29V) - advice going forward

Hi everyone - first ever post on the GMATClub Forum. Appreciate all contributors to this community - amazing stuff.

I took the official GMAT today and got a 640 (48Q, 29V, 5 IR). I was absolutely dumbfounded by how poorly I did in Verbal and was expecting to score somewhere between a 680 and 720.

Quick description: 30 y/o Indian American male with a BS in Chemical Engineering and MEng in Sustainable Energy Engineering; currently work for an Electric Utility as a Power Systems Engineer; ideally hoping to get into a top 10-15 school

Materials used: OG 2017, MGMAT Guides (including Advanced Quant, not including CR), PowerScore CR Bible, random material from the GMATClub forums

Practice CAT results:
MGMAT 1 (01/16/17): 590 (Q36, V34, IR 3)
MGMAT 2 (02/20/17): 650 (Q43, V36, IR 3)
MGMAT 3 (03/17/17): 640 (Q45, V33, IR 5)
MGMAT 4 (03/25/17): 640 (Q40, V37, IR 5, AWA Write 6)
GMATPrep 1 (03/31/17): 690 (Q48, V36, IR 5, AWA Write 6)

I took the Manhattan GMAT nine week in-person course and found both the organization of assignments and the pacing of problems quite helpful. The class was very engaging and the instructor (as I'm sure all from Manhattan are) was great. My main weaknesses were obviously in Verbal, specifically though CR and RC (main idea). I spent three weeks after the course preparing on my own before the official exam, which meant going through the remaining OG problems (not all of the Quant, but most if not all of the Verbal) and redoing questions I flagged. I was scoring > 80% on SC, so for Verbal I mainly focused on CR as a whole as well as RC main idea and inference questions. A few days before the test I went through all of the CR Challenge Set (from the GMATClub forums) and got at least 70% correct of each CR question type.

First off, hats off to all who can score a 6 or above on the IR. I can't seem to get above a 5.

Secondly, I feel pretty comfortable with Quant and have no problem scoring around a Q48.

Finally and most importantly, I need advice on how to proceed forward (I obviously need to work on Verbal). I feel as though my official Verbal score may just be an anomaly since it is my lowest Verbal score to date, and just to clear the air, I did not lose steam or struggle with fatigue towards the end. In addition, the fact that I scored at least a V36 on three out of my last four practice tests just boggles my mind.

I'm planning to retake on May 1st, which gives me a little less than three weeks. I am also planning to purchase GMATPrep Exam Pack 1 and go through the PowerScore CR Bible again.

Any help/advice/food for thought would be greatly appreciated.