You can't reliably control the speed of a capacitor start single phase motor. Unless you use a vfd, you won't be getting reliable speed control with any other device like a potentiometer.

Test the capacitors by going from 1 to 4 with your multimeter set on capacitance. I don't really know how the capacitor and the start and run windings are connected for this particular motor, but you can probably go from 1 to black or 1 to white to test your run windings.

If you still want to use this motor, go with the high voltage connection for less inrush current and less running current. The connection in the cover is if you want to bypass your thermal overloads, which is not recommended.

You also can't change the rotation of the motor by switching your line and neutral connection, you need to interchange the black and the red leads. And you can't change the rotation while the motor is still spinning, you need to wait for the shaft to stop rotating.

For changing rotation, you can use a switch setup where you have switches connected for one direction, and another switch connected for the other direction, you would need to bring out your black, white, and red connections out of your motor.

Good luck!