If it still works to ebrake, then the motor and the controller are both working correctly, as far as motor control is concerned.
It sounds like the problem is in the throttle, if that is what is not working. What voltage do you read at each wire from the throttle, with the black voltmeter lead connected to the negative wire of the battery? Test first with the throttle at zero, then test it at a few different positions up to full throttle.
You can test it at the connector between throttle and controller first, at hte back of the connector. If you can't reach that, you can poke the red voltmeter wire into the actual wire itself, so it pokes thru the insulation and into the conductor.