The "feeling" it's not really useful in the Gmat. First time i felt i did less than 500 and did 560, second time i felt i reached 650+ and nailed a 490.
Your material is fine, OG + OG Verbal
+ Manhattan Verbal Guides is enough to go over the 80th percentile for most people and I am pretty positive you just had a bad day:
you probably have not yet fully absorbed the verbal strategies (this process requires a huge amount of practice) and can not apply them under stressful conditions.
This is my wild guess, but if I'm correct with a little more smart practice you will reach 700+. Verbal is tough to improve, but in my experience it has a critical point, a peak, that wears out really fast if not reinforced or under stressful conditions.
I would'nt worry, you have it in you.
"The Burnout" - My Debrief
Kudos if I helped you