Looks tasty! I'm a sucker for buttered and toasted sourdough or rye.
This culture isn’t nearly as sharp as a San Francisco germ
Apologies if this is obvious to you, but IIRC from past reading, commercial sourdough achieves a higher acidity without needing to use the specific yeast via just adding acid directly. If you aren't dead-set on authentic, "the yeast do everything" sourdough, you could probably tweak sourdough to taste that way.
kagis
Okay, this isn't talking about what commercial producers do, but it is directly talking about increasing tang in homemade sourdough via the "directly-add-acid-to-the-dough" route:
Use Citric Acid In Your Sourdough
If you really want a stronger flavor in your sourdough bread, adding a little citric acid to your dough will help.
You can add ⅛ to ¼ of a teaspoon of citric acid to your sourdough. Do not use more than this amount because it will make your sourdough inedible.
You add the citric acid to your dough along with the water, flour and salt.
Note that this is something specific to the GSA, not a broad reversal of all federal layoffs.