Suggestions for bulk proof time and Cold Fermentation times

Hello all I've been experimenting with ratios and  bulk/fermentation times

I'm using a recipe that had 20% starter at a 100% hydration. My house is relatively cool right now (around 65F) when I mix the dough I add water at about 40F mix the dough, completed 3 set of folds every hour. Then I shaped the dough and took it into my basement where its about 57F and allowed it to bulk ferment from 10pm to about 9am. There was a rising almost to the brim of the banneton, and then I placed it in the fridge to cold ferment for another 24 hours. Got up the next morning and bake it at 450 for 50 minutes with the cast iron lid on and then 18 minutes with the lid off. The loaf didn't have much of an oven spring, and lost it's shape a little, was my bulk or cold fermentation too long? I've used a similar recipe but instead it was around 30% starter, followed the same procedure but baked it about 12 hours after cold fermentation had a slightly better result. It's currently cooling so I haven't been able to cut it open and sample to see if the flavor is good and see what the crumb looks like. But any help would be greatly appreciated for fermentation times!