Take the sol-vac off and put it in your tool box, it is dead weight now.
You have 2 idle speed screws, one for when the choke is on, the other for when the choke is off. On a warm engine, you should be able to back the warm idle speed screw out to the point the engine idles below 200 rpms. Set it to 650 - 750 depending on your driving style.
You should adjust your idle mixture screws for maximum RPMS and max vacuum ad idle (50 rpms lean of max speed is more proper).
Once initial timing is set, idle mixture set, reconnect the vac line to the vac advance and set the idle speed .
If you can't lower your idle speed, look for vac leaks at carb base, intake manifold, vac lines, brake booster, etc.
418 miles on 19 gallons of gas. Can't beat the BBD !