Ignition timing

After straining my back, I finally found that damn timing mark on my crank
pulley! It's a 1/16" hole drilled through the pulley right at the edge. This
is top dead center.

The manual says that ignition timing should be set at 15 degrees BTDC (8:1
compression ratio), but there's no marks on the crank pulley to indicate
that point!

Does this mean that you just have to guess as to where that is?

I turned the adjustment on the vacuum advance, but the timing mark didn't
move. (Using a strobe light). Does this mean that I have to do it the 'old
fashioned' way by loosening the distributor bolt and rotating it?

Thank you!