Fermenation lengths and help with oven spring

Thanks everyone for all the help so far, I've been doing a lot of reading in this forums to find ways to improve my loaves of bread.

I did a recipe I've been tweaking recently to adjust fo the previous results I've had. Problem is, oven spring is far from ideal, although better than before, but I'm not sure if its due to over-proofing or under-proofing.

What do you think?

Recipe

1. 10:07 AM Mix Levain
   1. Water Temp: 88F 
   2. Levain Temp: 78F
   3. Starter used was used 12 hours after it was fed, and the starter was on a 24-hour feed schedule. The starter had more than doubled, almost tripled, so I was comfortable using it.
2. 3:45 PM Autolyse
   1. Water Temp: 90F
3. 5:10 PM Mix
   1. Mixed Levain and Autolyse, plus salt and instant dried yeast
   2. Slap and Folds for 10 mins, I was actually really proud of the qualities of the dough after this set of Slaps and Folds
4. 5:50 PM Stretch and Fold
5. 6:15 PM Stretch and Fold
6. 6:40 PM Stretch and Fold
7. 7:00 PM Stretch and Fold, then straight to the fridge as cold bulk ferment.
8. 7:50 AM Next Day:
   1. Took out of the fridge, the dough was really cold (35F), but overall the dough increased around 2.2x times in volume (the container I have has marks so it's easy for me to check.)
   2. Divided and preshape
   3. Let rest for 10 mins
9. 8:15 AM: Shape into boules and put in bowls (with tea towels)
10. 9:00 AM First boule goes into the oven at 430F for 20 mins, the 430F until desired color in the crust (around 25 mins). 
11. The other boule was put in the fridge while the first boule was baking.

So I guess my doubts are where in my recipe I could improve, and also if it makes sense to proof the dough in their bannetons (or bowls) 1 hours if previously it was cold bulk fermented, or it needs less/more time proofing at Room Temperature.

Any help is greatly appreciated!

Thanks