I remembered I had an arduino with breadboard... I tested the wiring and instead of the motor I had 1 LED+resistor going from "motor 1st +" to "-" in the wiring diagram, and another LED+resistor going from "motor 2nd+" to "-". And then to be sure I switched the LEDs' legs and as expected it didn't shine then but when switching positive and negative input the breadboard the first LED went dark and the other one lit up.
I'm going to buy a car fuse assortment box for mini ATC fuses (small flat car fuses), that is the type that the motor controller has. Because I agree that 25A is probably to much. 10A or 15A will be better. You wrote "single common - lead feeding the motor". Do you mean I anyway should have an extra fuse after the motor (the "-" connector of the motor) or do I get away from this by changing the fuse on the controller.