From a 36 hrs baguette mishap to a gorgeous 25 hours batard...and a question

On a sunday morning, I set out to try the 36 hours baguette recipe from txfarmer. Eight hours later, as I was re-visiting the procedures of this recipe, I noticed that I'd made a mistake and I immediately ran to the fridge: the levain is supposed to be mixed in AFTER the flour and water have hung out in the fridge for 12 hours.  However, I mixed levain, flour and water all at once and put the whole thing in the fridge.  Did I just create a gigantic levain?

I took the mixture out of the fridge right away, added the salt, and let it fermented for about 3 1/2 hours (S&F in between). Then I pre-shaped, shaped, proofed at room temperature for a while and put it back to the fridge. (I decided to do a batard shape instead of baguette because at this point, I had no idea how the dough is going to perform and I didn't want to put much effort in shaping)  However, due to the earlier mistake, I wasn't confident to let it retard for another 24 hours.  The dough retarded overnight in the fridge and I baked it in the morning.

The dough surprised me. It rose nicely in the oven, sang beautifully when it came out, and tasted great.  Happy ending.

A few cracks appeared after it finished singing.

Crumb shot.  Tender and chewy at the same time.  Got a sour note due to long fermentation.

So now I wonder...how to determine when to add levain to the flour mixture?

Thanks

Michelle