Each revolution should advance one spot, up to the 100K. There is a switch in the spin out to count the revolutions. It takes the heavy plunger spring to make enough revolutions.

On ball launch, the ball should circle the spin out ramp passed the 100,000. This allows for the skill shot to come into play. Check tabs on spin out ramp. If its moving around the balls momentum is slowed. Also make sure the shooter rod is hitting center of the ball. I have mine set a little above center to give it some top English. This allows more speed into the spin out. A good cleaning on the spin out ramp also allows the ball to glide faster. Mine usually will go through the scoring once and back to the 75,000 on full plunge. Your correct that the multiplier changed with each ball..
Good luck

Also take a look at how the plunger is lining up with the ball. If the plunger is off center, the ball will not have full momentum. I found on mine that the playfield brackets in the front needed to be shimmed a little.

Look at how the ball aligns with the plunger. You may need to adjust the shooter rod so it aligns with the ball properly. Also the springs on the shooter rod may need to be changed. Newer ones on the front may be too big or too stiff.