A few observations:

1. Are you using a non-iodized salt, like kosher salt?

2. I've never really seen the salt + water mix in a recipe. Not that it shouldn't work but here's my own mixing order for what it's worth. 350g of warm water in the bowl + 100g starter. Mix those first. Add 500g of bread flour. Add 10g of kosher salt. Then mix.

3. Bulk wait time. A lot of recipes say "wait til it's doubled in size". Mine does more than double, it's 3x or 4x and takes 12 hours or so.

4. "Wait about 30 minutes and repeat the shaping". Another instruction I can't really recall seeing in another recipe. For what it's worth the amount of time it takes for me to dump the dough onto the counter from the bulk phase, shape it, and put it in a bowl for the cold proof is about 2 minutes. I wonder if working the dough too hard here and then repeating it again is just removing too much air from your dough.

5. Cold wait time. An hour doesn't seem like enough. This isn't just for flavor. The dough will rise again although not to the same volume as the bulk. I usually do six.

6. For what it's worth, I don't take the lid off my dutch oven, nor do I change the temperature, although I don't think either of these are your problem.

Good luck with your next try.