[mr0077]

AZ, what you just described ("The vacuum reading rises steadily as the RPMs increase. When shifting, between gears (clutch in and throttle off) the vacuum will jump up to 35" Hg then drops down to the 10" Hg as the next gear is engaged and throttle is applied again.") is not possible; an absolute vacuum is 29.92" Hg, so you can't read 35" Hg. If the gauge is reading high by 10" Hg, you would get the readings you recorded. When you get around to working on the vacuum side of things, I would get a second gauge to check your readings.

The advice above is very good and complete, you should concentrate on the mechanical side first; once set, then fiddle with (or eliminate) the vacuum advance. It can improve mileage, but does not improve power.