The oven looks cool and the pies look good. I've made plenty of D and F pies in my day and still do occassionally. The chewiness is likely in part from the over mature starter as you suspect. The acids break down the dough and toughen the crumb accentuating any toughness from over mixing as well. The breakdown, along with a long ferment also cause the dough to become super slack. Before you pitch the old flour you might try a batch with a much younger starter. Use only about 10% seed for the new starter, let it get active (6-8hours at room temps), then dump half, refeed, and when it gets active again, it should be okay to use. I make it a habit to taste the starter before using to make sure it has very little acidity. If you continue having trouble with the starter, there is no shame in using CY or commercial yeast as well until you feel comfortable.
Also, a 10% starter will take around 12 hours or soon at room temps of 75F to fully ferment the dough. For a 48 hour dough, I believe Craig uses around 1.5% starter at 65F. So even if you start with a young starter, if you let the dough sit too long, it will over mature and ruin the dough. You might consider using less starter, shortening your fermentation times, or both.
Let's see some more pictures. And honestly, I'm still fumbling around with everyone else.