I did just make a major breakthrough this afternoon, I got it working...kinda..sort of...mostly.
Before when I it the Start button, the score reels would reset then Player One started racking up points on the 1,000 point reel and wouldn't stop until I turned it off. I looked for a stuck switch without luck for quite some time until I found two switch lugs touching each other on the 5-bank drop target housing. Pulled them apart and that problem was fixed. It now starts and plays a game, all switches, lamps and chimes work.
The machine still is confused though. At power up, only the score reel lights for players 1 and 4 light up, 2 and 3 do not. I believe all four players' reel lights should be on. When you start a game, player 4's reel lights go out and player 1's stay on as they should. You can press the start button 3 more times to light all four players. But when you drain player 1, ball 1, the machine does not advance to ball 2 (if playing a single player), or player 2 (if playing multiple players), much less players 3 and 4.
I think that I have the switches on the AX, BX, DX, and Q relays adjusted properly. I think. Both of the large switches on the coin unit are closed for one player operation.
BTW, I wanted to thank you for explaining the diagram for the Score Motor switches to me.
I'll try and explain it to anyone else who doesn't understand it. (Lord, I hope I'm not the only one)
The switch numbers in the diagram in post #5 above do not refer to the actual switches themselves, but to the HOLES in the metal bracket below the rotating disc. Notice a double line on each end of the switch number hole in the diagram. That is where the white spacers are at the ends of each switch bank, opposite the end where the bakelite spacers and screws are. For example, switch #4 is the one with two switch stacks just to the right or the large hole in my pic of the rotating disc. Switch #1 is the double stack at the bottom left corner of my pic, perpendicular to switch #4. Switch #2 is parallel to #4 and switch 3 is right next to the small hole in my pic.