Vacuum is "ported" so no vacuum at idle to the advance. My truck had a sticky power valve and after I fixed that it worked much better. The vacuum advance will move the whole distributor when you blip the throttle. But the port for the vacuum is not open until the throttle is opened. The dwell is a bit weird as reported. Be certain that you are on the right scale. And the correct voltage. Also check that the coil is wired correctly. Ignition to + and - to the points. Points at 0.027 is rather large. Idle mixture can be set with out a vacuum gauge. Not perfect but quite close. When the timing is set. And the idle speed is set. Turn the mixture screw in until the engine starts to stumble. Just as it starts to stumble. You can feel it, then turn back out 1/2 to 3/4 turn. If it still has a bad stumble then you might need to clean and rebuild the Carb. Get the points and dwell sorted first. Others will have some thoughts to help.
