OK, the following is largely from memory, but I believe it should help. If you run into any snags, just post an update on the issue you are having. Also I realize you have already done several of the steps below, I'm just including them for completeness.
The spotted number depends entirely on the position of the wiper fingers relative to the phenolic disc containing the rivets. As you know, you need to coordinate the position of the wiper fingers with the position of the plastic number wheel. The following steps are one way to do that. This is not how they did it at the factory, but it should work for you.
As you noted, the top clamp for the plastic number wheel and the bottom spider for the wiper fingers are both held on with hex-head set screws. The first thing you need to do is make sure that these set-screws are cinched down really tight on the central axle of the unit.
The remaining fine adjustments are made with the three adjustment screws on the top clamp and on the bottom spider. The next adjustment to do is to set the wiper finger position so that the wipers land directly on top of a set of rivets when the unit is in the stopped position. This adjustment is done with the three clamp screws holding the wiper fingers onto the spider. It really doesn't matter which set of rivets you select, as long as you get the wipers and rivets lined up. It's usually a good idea to manually actuate a spin on the unit several times, and confirm that the wipers always land over a set of rivets when the unit stops.
The final adjustment is done with the plastic number wheel. Start a game and manually actuate a SPIN until the machine spots one of the numbers that is only shown on the number wheel ONE time (1, 3, 4, 6, 8, 9, or 11). As soon as you have the unit in a position where one of these numbers is spotted, hold the unit in that position while you move the plastic number wheel so that number is in the selected position. Then tighten the clamp holding the plastic number wheel in place. This should synchronize the whole wheel.
Hope this helps - TimMe