I can’t control a brushed DC motor using Pixhawk, Sabertooth motor controller, and a PM07 power board

I tried PX4 on a rover a while ago, but never got it to work as I wanted. So, yes, I recommend ardurover.
The dip switch wizard says:
1 off
2 on
3 off
4 off
5 on
6 off
for lithium power, microcontroller PWM control, independent mode, linear response.