I'd recommend that u stop Kaplan Q bank now
If you do well in NBME then proceed with Kaplan Q bank and never bother with what score u get
If you do bad in NBME then I suggest you read again your primary materials
I think the problem is that you are used to UW and so when u switch back to Kaplan u find difficult
The difficult of Kaplan questions are different from UW
In UW, the difficulty is in the case diagnosis and once u get the diagnosis you'll know the answer while in Kaplan it's more direct questions with no twisted clinical features however they mess up with the options making them all looking correct
I heard that the real exam is a combination of both difficulties
i have heard people saying that kaplan is much easier than usmle world but i guess it is because you are used to the way usmle world questions are asked...so it seems difficult hope you pass your exams..