"Romp advance " should mostly be handled by your mechanical-thus why you figure total advance with vacuum DISCONNECTED and RPMS above 3000.

Cruise is high vacuum low load situation and vacuum advance gives that additional timing ABOVE your mechanical for economy and lean burn.

"I see!" said the blind man.  Thanks Steve.

Flog that horse:

 

 

Here's my Cyber Monday quest.

 

Those are great tools!  You can accurately read rpm as well as advance the timing light to read the mark nulled to 0 on the scale at the damper pulley.

 

The cable is long enough to read rpms from the passenger compartment while driving ... works great when also reading the O2 in the passenger seat in real time road tuning.