Bob, I haven't been following this thread super closely but did want to say that if you replace 35% of your current flour with AP flour and kept everything else the same, you would essentially have a wetter feeling dough. Assuming, you were using BF, AP is a weaker flour and absorbs less water. This is equivalent to upping your hydration. So in a sense, you will be able to see if you can get a crispier crust by upping your hydration, just by replacing 35% of your flour with AP flour. My feeling is that you will not but let's see what happens.
Also I don't know if this has been mentioned, but a tough leathery crumb is usually due to over mixing. You can make a wonderfully soft crumb using AP, BF, or HG flour. It all depends on how you mix it, how much you mix it, hydration level, other crumb softening ingredients, and how you bake it out. If you are using a food processor to mix your dough, it is really easy to over mix. You can easily over mix the dough and still end up with a tough crumb even afrer replacing 30% of your flour with AP.
Also AP flour, and a higher hydration will work against a crispier crust. If you want a crispier crust this is how you can achieve it. Either use straight BF or HG flour, drop your hydration by a few points, cut your food processor mixing time down dramatically. It really only takes a few 10 second bursts to sufficiently develop the gluten. Btw it's easier to get a crispier crust using the food processor to mix your dough rather than a traditional mixer, but it's also easier to over mix and get a tough crumb.
Good luck and do post up some more pictures of your experiments.