The brake switches are not just for regenerative braking, they also cut the power to the motor
(and disengage the cruise function) to ensure it stops pulling when you want to slow down. If your throttle was to be knocked and damaged, you could end up with the motor stuck at half power
(or even full power) and no quick way of stopping it apart from disconnecting the battery power.
You might want to consider using the on/off switch on the throttle to operate the brake function on the controller in place of the brake levers. You could then use the horn or cruise button to momentarily operate the reverse function when needed.
Take a look at
this post and
this video for more details on testing the operation of the hall sensors.
The reason why I suggest checking the Hall sensors in the motor is because they all share the same +5V supply as the throttle Hall sensor.
If the +5V supply wire was momentarily subjected to high voltage feedback from the throttle Hall sensor when it failed, then the high voltage may have damaged one
(or more) of the three Hall sensors within the motor.
As the 5V voltage regulator in the controller appears to still be working, it seems to have survived the short burst of high voltage
(if it was subjected to a momentary high voltage when the Hall sensor failed).
If all three of the motor's Hall sensors are still working correctly, it will hopefully be just the failed throttle
(or perhaps one of the programmable settings) that is preventing your motor from running.
Alan