The boring stuff.
70% hydration, 200g white starter 50/50, 600g water, 900g King Arthur White Bread Flour, 26g salt,
Mixed in my KitchenAid until everything comes together. Then covered for three hours at 69F. Applied two stretch and folds. Then placed in refrigerator for 28hrs. Placed in the proofer at 71F for for eight hours with two more folds in the first two hours. Preshaped and the shaped loaves. Let them rise at 71F for five hours.
The interesting part.
Placed the the covered loaves in the refrigerator for three hours to cool it down. And then I sprayed ice cold water on the loaves before baking them. And we have blisters!
The Boule was baked using the cold oven method in the dutch oven at 465F/240.5C (Oven gets up to 475F/246C at this setting) for forty minutes covered then fifteen minutes uncovered.
The Batard was then baked on the preheated baking stone with water in the pan below for more steam.
As usual I'm chasing better oven spring, but I'm excited I can get blisters without having to do an overnight rise.
I would reduce your salt significantly. You are currently at around 1.4%. i would get it closer to 1% or between 14-17 grams. The salt will significantly suppress your yeast especially if it is a sourdough leaven.
Suspect this will be a big part of you not getting the spring that you are looking for. Taste will minimally be affected... If anything you will be over salting your dough.
Good luck. Let me know how you get on... I have some further thoughts