Advise needed, do I postpone and by how much?

Hi everyone, this reddit page has been very helpful so far and I was wondering if you wise usmle step 1 takers can give me advise!

Friday I took NBME form 30 and I scored only a 49% on it, aka by far not ready. Saturday I did the Free120 of 2024 and I scored a 60% on (only one day after and I basically hadn't really studied in between). Can anyone explain to me why there would be such a big difference between the two scores and which one is the best representation on how ready / not ready I am? I know the broad idea is to score at least 67% or higher to be ready, but there's quite a big difference between 49% and 67% vs 60% and 67%...

My exam is scheduled 9 days from now, July 30th, but I think I should postpone huh? Anyone any idea or rough estimation on how much I should postpone it by? I've been studying for an average of 10hr/day, which I could continue for the rest of this month or as long as I need.

Thank you so much!!