First, the "air leak" at the brass fitting on the choke housing is normal, as the electric choke fits to the original exhaust heated choke housing. The air leak is actually an inlet to allow a metered amount of cooler air into the choke to keep the electric heat stove from overheating to failure. Don't block it off.
The full manifold vacuum sourcing for the vacuum advance is what you want, BUT, if the advance isn't set up correctly to meter the number of degrees it delivers, the engine will over time, and idle rpm's can rise above a proper setting. A pimple procedure, and either a home made degree stop, or a crane stand alone adjustable stop can be added to stock and adjustable vacuum advances, to get them dialed in properly.
If you want a vacuum advance stop info package, they are absolutely free, and show how to do it right, send an email asking for them to: [email protected]
The stop methods work on both point and HEI distributors, and are not expensive to do.
Then, you can set the degrees to supplement initial timing, to attain IDLE settings of 20 to 24 degrees, which the engine will like. This would be an initial setting, with full manifold vacuum advance degrees combined to give a total IDLE timing.