Well changing the pump timing is not going to change the chain stretch. That is a wear factor. How did you read the stretch? Always turning engine in the same direction? By the crank bolt?

I believe black smoke is a sign of injection being retarded. I would try marking the flanges with a pin punch so there can be no confusion. Try your car with the pump moved to between the two current marks. The mark you started with and where you landed up. If no longer pinging and smoke is gone stay there for now. Another way to look at is you want that pump as much toward the original mark if I read your marks correct. That being towards the block consistant with that pinging not being present. Half way between is a good place to try. . It may be just fine.

Really to do the stretch measuring properly you have to use the dial gauge method to be accurate. Make sure to read the postings on checking chain stretch as well. There will be lots in the archives.

Congratulations, You learnt something by tackiling it yourself. From now on it is easier. I suspect a few members are mulling over your results. I am not perfectly clear in my mind myself. If you did the timing all alone and the hand primer was leaking bad there might be a little discrepancy entered into the end results. The loss of the pinging noise does mean the pump was too advanced since it is now gone.