“PAIN À L’AIL DES OURS” Daniel Leader (Living Bread) - Advice sought

As a novice baker, I decided to try my hand at Daniel Leader's version of PAIN À L’AIL DES OURS. I’ve spent the first 7 months (of my residential home baking career) baking from Ken Forkish's FWSY with great and evolving degrees of success, but was I too ambitious to take on such a recipe?

 This was my first attempt using a sourdough starter and rye flour. Due to availability, I substituted the suggested type 65 flour for a type 55 organic all purpose unbleached flour (Milanaise). Is this a faux pas in bread baking?  This was also my first attempt at shaping a bâtard and cooking from a stone. After a 14 hr retard + 2 hr warmup + 45 min pre-shaping rest + 90 min proof + scoring, I was surprised to see how the dough almost instantaneously lost its structure.  It became more blob like than bâtard. I initially felt I had enough tension but as often as been the case, I tend to lose the intended shape structure and the intended elusive “ear”. Why? Finally, I adjusted the baking temps  (10 mins @ 500 + 15 @ 475) to accommodate for an old rickety stove. Final texture: soft crust,  not as smooth or uniform as I hoped for.  I realize I can’t compare my Creuset Dutch Oven to a $25 Home Depot pizza stone but is there such a thing as a high quality stone? I could have baked much longer but as a rule of thumb, I always like to follow a recipe guide from start to finish the first time. Rise: lower than expected. Could I have used my started too early?Open crumb: open to the public to decide… Bread baking has been a fun and exciting pastime during this interesting year of ours.  I aspire greatly improve my knowledge and skill and thought that perhaps it was my turn to raise my hand for advice from this passionate community.  I’m grateful for any feedback and or commentary. Recipe snapshot:“LIQUID LEVAIN STARTER 6 to 8 hoursAUTOLYSE 30 minutes”“KNEAD 13 minutesRETARD 8 to 12 hoursWARM UP 1½ to 2 hoursREST 45 minutesFINAL PROOF 1½ hoursBAKE 25 minute” LIQUID LEVAIN STARTERLiquid Sourdough Starter20 gWater51 gType 65 or equivalent flour (11 to 11.5% protein) - Substitute type 5551 g” FINAL DOUGH“Type 65 or equivalent flour (11 to 11.5% protein) - Substitute type 55506 gWhole rye flour101 gWater364 gSalt13 gDry instant yeast3 gLiquid levain starter121 g spring onions, coarsely chopped90 g