My 1st Tartine bread (failed...)

yeah...just like the title...
I read an article in here about sharing ur learning experience...not all the good ones but the...failed ones as well...
so, here it is.

Recipe
Bread flour 900g
WW flour 100g
Water 750g
Salt 20g
Levain 200g

I followed the recipe exactly and after 3 hrs bulk rise (with stretch and fold every 30 mins) I retarded the tub around 18 hrs (from 11:45 pm to 06:00 pm, I have a full-time job -_-~)
divided and pre-shaped twice every 20 mins before the final shape (really really sticky and slack)
dusted the basket with bran flour (a sorta bread flour with lots of bran~)
final rise for 2.5 hrs. (I was making soup with windows close, so the ambient temp was higher, I did the finger dent test and my guts told me "its time to bake")

there are 2 factors that I'm not really sure about.
1 is the flour thing, like what I mentioned before - summer time - high humidity - quality, I think using less water will fix this problem
2 is the major one - starter and levain.
I discard 80% and feed my starter around 11 pm with 50/50 of BF, WWF and equal weight of warm water.
around 7 am, I do the smell check, not very sharp but just a little bit sour and a bit nutty, that's the levain I used.

yeah, I still have the other half and will continue to bake. maybe after my 100 loaves, I can sum up some tips~
So, guys~please give me some advise and let me know what you think what went wrong.

Thanks

Jason1876