A Word About Durum Flour
Durum Flour does not suit a very long ferment even if you drop the starter percentage. I think it would be best to use a not overly ripe preferment and no less than 20%. Over fermentation is not the problem here. I think the dough begins to breakdown just because of the long soak alone. Durum flour, over time, will begin to leach the water out.
My recommendation would be...
1: A high percentage of pre-ferment so the final dough doesn't take so long.
2: The pre-ferment shouldn't be overly ripe as since it's a high percentage one wouldn't want that degraded either.
3: Since it has a tendency to leach water perhaps aim for a slightly under the "perfect" hydration.
4: Go easy with stretch and folds as the dough is further along the ferment. Don't ruin the structure of the dough. It does not gain it back like a bread flour. When adding things in do so at the very start or close to. This way they're incorporated already as your building the strength and structure of the dough.
Sorry but see my post from last week of my 100% Durum. I used a 2 build levain and an overnight retard with no issues. I do use a fairly large amount of preferment but I also had no issues doing 3 sets of S&F. I did build the gluten fairly well with my mixer. I’ve never had an issue leaching water so I’m surprised you observed that. Just my 2 cents for what it’s worth.
Sounds just perfect. I think we're entirely in agreement. And an overnight retard, as supposed to a very long room temp ferment, also sounds like a better idea.
I don't think your recipe does compare. The accompanying post will explain better. I even recommend Alan's two build levain as in his original recipe.