I believe that if you had a manifold vacuam leak, the engine would not idle. Since you've tried your accelerator pumps, and you said that your centrifugal advance is okay, it still points toward your power valve(enrichening system). Have you been able to identify the portion of the carb(s) tha provide low vacuam enrichment? With the symptoms you continue to describe and the things that you've checked it still seems that this is where you problem lies.
Don't get discouraged. I've been through things like this before, and with my personality, they continue to gnaw at me day and night. Hang in there and keep investigating.
I have to run right now for a meeting which will last most all day, when I get a little time, maybe tomorrow, I'll reread all your e-mails regarding this problem and try to think it through some.
HANG IN THERE AND DON'T GIVE UP