I wasn't able to see the video (problem on my end), does the choke ever completely open?
The timing mark won't be visible if the vacuum advance is hooked up to a manifold vacuum source,
If it was disconnected and plugged, the timing tab/damper line may be off; there were three Gen I tabs/dampers
that may be confusing the issue.
will allow you to be sure the timing tab and damper are correctly indicating TDC.
MAKE A TIMING TAPE
to see what the total timing is, w/o needing to use a dial back timing light. You can also buy a timing tape, get one that matches the diameter of your damper.
The image shows the correct orientation of the timing tape:
Because the distributor is running the engine, I doubt the drop did any real harm. I would expect a no-start condition if the module or pick up coil had been damaged by it falling. Sometimes modules will run fine cold but give problems when they're hot. The pick up coil can exhibit erratic behavior if the wire inside the insulation is broken from the movement of the advance plate on the distributor.
If you need it:
an exploded view of an HEI distributor.
is a description of an HEI rebuild. HERE
is another HEI info/rebuild page.