Need some help with my timing curve.

That timing table is great to see. I'll have to look later at Richard Holdener's vid that you reference.
At the drag strip, or even on a dyno, a little more timing can pick up some power because the engine isn't heat soaked like it gets on a long trip or road racing, etc.
I think with the distributor, unless using an ECU with some predictive ability, we can count on losing a degree or two every 1000 rpm increase. That's another reason I don't like the hard stop.
I completely agree that it may be that the advance limiter plate may be useful if the situation warrants. Testing with the plate installed we may not get to learn the characteristics of this long spring/advance slot combination.

In sum I think we are in complete agreement, just looking at it from different perspectives.