I hate to make recommendations for somebody else's heli. But what I would do with a governor is just set a channel 8 switch on/off. Then use something like this for the throttle control
To explain what the above settings will do:
You arm and throw the throttle switch. The 500 setting for the setpoint is the governor signal at 50% rated power. The ramp time is 19 seconds. So it will take 19 seconds for the signal to ESC to go from 1000pwm to 1500pwm. When the runup time is complete (20 seconds) you are ready to fly.
For a smaller helicopter with less inertial mass in the rotor you can use a faster ramp time. For bigger ones I like to use more ramp time so it's gentle on the runup and doesn't do anything radical. And it also gives you 20 seconds to observe the heli during spool-up in case it starts to vibrate, shake doesn't sound right, etc. - just flip the throttle switch off and abort it.
I'm just guessing on the 50% signal (H_RSC_SETPOINT, 500) because it looked like you were using 1500 pwm in the BIN logs on RC8 out.
Now, be aware that some ESC governors will not work below a 70% throttle setting. If you have one of those and the minimum the governor will work at is too fast for the headspeed, then you will have to disable the governor and use a MODE 1 with a mix from the radio, or a MODE 3 with a V-throttle curve set with the H_RSC_POWER params.