Regarding the NGK caps, take a ohmmeter and make sure their resistance is same as the ones your replacing. I had a hard learned lesson a few years back. I installed a set of Nology coils on my bike and unknowingly used caps that had too much resistance. The bike was miss firing at higher RPM. I put the little stock coils and caps on and the issue went away. I eventually got two RS125 coils and things work great. My bikes pretty well sorted, but retired and literally on a shelf.

I think you can rule out crank seals at this point based on your measurements.