Problem 1: You'll need to check the switches that control power to the bonus kick out hole. It looks like this kick out hole is called the "Top Eject" hole. A switch on the auxiliary top eject relay sends power to the top eject hole solenoid. If this kick out hole works when bonus is showing, then you would want to look at the bonus unit zero position switch. Make sure the switch is clean and adjusted properly.

Problem 2: This sounds it might be an issue with the coin unit. Manually advance and reset the coin unit to see if it easily clicks into each of the four positions. When you start a game, confirm that the coin unit is in the one player position.

Problem 3: You'll need to look at all the switches and coils in the credit button circuit. Find the credit button switch on the schematic (grid D-3) and check the switches going toward the credit relay. Make sure the switches are clean and adjusted properly. Also, check the condition of the credit relay coil...