Ok, my first feedback on this updated script is:

After trying it on the 97 SE TB version and 2004 SE DVD of ANH, this time it does indeed lock black and white level it seems, but the saturation comes out way too strong at times.

Could it be that the difference in gamma between the two versions is confusing this script? Or is it that the resulting chroma of this script is matched to a luma difference which is now ignored since the black/white levels are locked?

I'm going to try it on some sources that match a bit better in luma.