Slant Six has No power. will not accelerate

That your mechanical advance seems normal. It advances ignition timing as RPM's increase.

If the vaccum advance dashpot is not leaking, then did you look down inside the distributor with the rotor button removed and see that the plate (on which the sensor or points are mounted) did or did not move when you sucked on the vacuum hose? This plate should move when you suck on the hose, not the rotor button.

There should be a little bar from the vacuum advance dashpot that connects to that same plate; as I recall, the bar is under the plate on this distributor so may be hard to spot. See if you can spot the little bar and if it moves with the sucking or not; it should move towards the dashpot with vacuum.

The plate can be stuck/frozon, or the bar disconnected from the plate or broken inside the dashpot.