Is the Pertronix a capacitive discharge ignition? If so the secondary-voltage rise-time is much faster than with a transistor fired coil setup; in which case you will need less advance at higher RPM because it will fire the plug sooner in real time which means more degrees advance the faster the engine turns. So I'd be conservative with the initial advance even if it seems to idle better if you have a CD system. I run a MSD, which is a CD system and I use the factory static setting according to the flywheel, then dial in 5 deg with the octane selector. Slight bog off idle but otherwise has run fine these twenty years.

As far as vacuum at idle, I'm at 2500 ft elevation and have a hotter cam than stock so my vacuum readings will be lower than yours but I have about 14-15" at 700 RPM. Pops right up when it goes above idle. By 1200 it's about 19-20" hg. If throttle response is good and it doesn't ping in hot weather when you lug it, I'd say you're good to go.

1951 3800 1-ton
"Earning its keep from the get-go"
In the DITY Gallery
1962 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.