@saintofinternet,
The Pixhawk ArduRover firmware will put out a standard PWM signal where 1500us is neutral, 1000us is full reverse, and 2000us is full forward. This PWM output works with RC car ESCs that support forwards and reverse and Sabertooth ESCs that support forward and reverse.
Your ESC appears to accept PWM input, but seems to require inputs for CW and CCW rotation for the brakes which is not available from the Pixhawk servo outputs.
Regards,
TCIII AVD