Joe, your distributor should be setup to give you 20 degrees advance with 32/33 total mechical degrees in the 2500-3000 RPM range, assuming 12 degrees advance dialed in at idle. Your advance should start to come in at about 1000 RPM, as the engine will idle lower than this. That will be very close when setting up the mechanical curve.
The vacuum can should have around 8-10 degrees of additional advance and be plugged into the manifold port. This should give you a smooth idle assuming the carb is adjusted correctly and good part throttle performance.
You can not crutch one type of advance curve with the other, vacuum versus mechanical, they perform totally different functions. Vacuum advance is load based and mechanical is RPM based.
As to your question about cruise RPM, the only way you can have the best of all worlds with optimum timing at 1800 RPM is via a totally programmable ignition system. Not worth the expense on an application of your type.