Your vacuum connection is not good location for a vacuum reading (for timing) at idle (the reason is posted by others, above).
Set the idle speed (to a low rpm, steady idle, if you do not have a tachometer).
Connect the vacuum gauge to the port that provides vacuum to the wipers.
Then adjust the distributor/timing to obtain maximum vacuum;
then, adjust the carburetor to obtain maximum vacuum.
Then, reset the idle speed (and readjust the timing & carburetor).
Take a test ride.
Finer adjustments for timing are nice (and can-be/should-be done later), but do the above first and go for a ride.
