Your distributor looks like it's installed 'incorrectly'. If you bump the distributor a tooth forward (remove the distributor and turn it clockwise 1 spline) and it will only fire when the adjustment is fully retarded you have an issue I have run into before and can be remedied by changing the firing order. Remove the distributor and install it 180 degrees out (rotor button facing #4 lead on the distributor cap) and swap the #1 lead location to #4, then swap #2 location to #3. I'm not 100% sure why it happens but for some reason after head work the distributor ends out being 1/2 a tooth out. If the test where you have removed the distributor and bumped it a tooth and adjusted the advance didn't yeild a result the issue is somewhere else (maybe faulty vac advance unit on the distributor or as suggested vac lines)