I don't know if this helps or is indicative of anything, but my GMATPrep 1 Verbal was 44, and my GMATPrep2 Verbal was 38... I think GMATPrep2 Verbal was a bit harder.
As for how many you get wrong versus the score, you cannot compare like that because it all depends on the DIFFICULTY of the questions you're doing and missing.
If you feel that you're ready, and you've done all the questions you can and understand your mistakes, I would give it a go and not reschedule. What were your other test scores like? The more info you give us, the more we can give you advice to decide.