NBME's predict your scores really well, there's only a 5-10 point differential, from what I know atleast , (i.e, if you're scoring 200/194 you may get anywhere from a 190-210ish on the real thing).
I've only heard of two rare instances where a person was scoring really high on NBME's and failed the real thing, and heard only one person who was incredibly borderline passing.
But since post-poning the exam isn't an option, I suggest you try to read FA through & through and Uworld to the best of your ability.
Hope this helps, good luck.