I’m just a home baker but I’ve made this a bunch.

Dutch oven should not be preheated in the oven – I line with parchment and let my loaf proof in it one final time before baking.

Final proofing needed after shaping? Yes, always.

The high temp is accurate . You want to create steam quickly. My oven runs very hot so I have to turn down to 450 though, so may need to pay attention to your oven. But basically, follow the baking instructions in the recipe step 8, not the narrative.

Another reason such high temperatures: you are creating a crispy, crunchy crust.

Best of luck!

I’ve made this recipe many times now. I always allow to rise a really long time. The final proof (after shaping the loaf and before the bake is the only proof you need to worry about in terms of not under or over proofing. I usually do about 45-min to one hour for the final proof, which I do in a parchment-lined Dutch oven with lid on. But depending on the heat of your kitchen, you may need less or more time. Use a finger test — when depressing your finger lightly into the dough, does it spring right back? It’s underproofed. Does it leave a deep hole that never fills? Overproofed. You want your dough to be puffy but to still fill your finger indentation back in at least partly. At that stage, sprinkle with more semolina or bread flour, make a couple slashes, replace lid and bake as directed.

When you say loose, do you mean your dough was too wet? In this case, sounds like you need to add more flour. Are you using a kitchen scale to weigh your ingredients? Highly recommend!

Yes