From what I read in your post you do have several flaws in my opinion.

1) The fact that you have a good GPA and come from a background of Engineer tells us about how you could score during the gre almost nothing.

Yes, it is true you can have a solid quant background. However, the test is NOT, I repeat for being sure, the test is NOT a test in which you have a ZERO SUM. And I assume you do know what that means without delving too much in this concept.

2) You based most of your preparation on the material which is NON-official. That material is good only to build your stamina and confidence nothing more. The Powerprep is KING. it judges you and your performance before the test center.

3) Studying vocabs serve to score well on the verbal part like the dawn. As soon as the sun rises the nite is already over.

To score well you have to have a strong, powerful, rock-solid understanding of the sentence and/or the passage in front of you. I.E. what are you reading you understand it ?? you know the sentence ?' do you recognize the shift in it in terms of the possible time frame or punctuation such as a colon ??? what is going on in the sentence ?? do you see the relationship between/among the different part on a different level ??'

4) which is your strategy ?? what questions, for instance during the quant side, do you tackle first ?? PS or QCQ ? with which you are more confident ?'
Do you think have stamina ?? endurance ?? time- management ?' did you care each of these aspects ??

4A ) Specifically for the verbal side: do you read the passage or you get lost and jump to the questions and then back to the reading ?? back and forth back and forth back and forth ?? for SE do you are able to pair the answer choices ??' for TC which strategy do you have ??

This k about these questions and probably you could improve your score.

Do you have the official report ?' what did you get right or wrong ???

Regards