I think you over thought the process. The shaft diameter is 0.625" The taper on the shaft shouldn't mater as the taper in the flywheel is the same. The shaft will turn at the same rate no matter where the key is located on the shaft or taper. Ultimately you talking a shaft dia of 0.625". If you use that diameter to calculate the degrees of rotation you would divide the circumference of the shaft by 360 degrees. Each degree in that case would be 0.0022". It becomes a larger number if the crankshaft is a larger diameter.
I don't compensate for the sloppy needle bearings.
Make sense?
While I was typing this I forgot about my hotdogs on the stove. They done got blowed up.