So very stuck...

Vacuum advance is an awesome tool. Hooked to ported vacuum it is used for fuel mileage and economy, hooked to manifold vacuum it is used to bring in lots of idle timing and cruise timing. In my opinion you are over thinking this. Leave the vacuum advance plugged until you get a good baseline tune in the thing and a better understanding of how the systems operate. 36 may still be a little too much all in timing for a heavier vehicle, I’d set it to 32 and test. If no pinging, try 34. The difference between 32 and 36 is not very much hp, but the window of saftey is much bigger. You don’t need to run it on the ragged edge.