Vermont Sourdough & different flours

I'm continuing my efforts to bake a better Vermont Sourdough (with 10% Whole Wheat), and here's a followup. I baked the below with a 100% hydration starter, but adjusted the dough hydration of course:

I believe this is quite a bit better than what I was doing 10 days ago (but of course, a ways to go). The big difference: till last week, I baked with 100% KA AP flour. This week, I baked with 25% KA AP flour, 75% Bob's Red Mill bread flour. I could feel the difference in dough strength, it was holding up a lot better with BRM. IIRC, BRM has higher protein content. Hans and Dan pointed out over the last few weeks that my problem could be protease, and it all probably makes sense - I am hoping this is the right explanation now, finally. Bread was of course a bit chewier than the last few weeks too.

Having said all this, I have a few of questions I'm hoping someone can help with:

- Do others baking with a levain build at 100-125% hydration have similar issues with KA AP flour?

- Or is it that, somehow, my starter is causing extra protease activity in the levain build?

- Sometimes, I like bread that's not at all chewy. If I use BRM, it does become chewy. Assuming that my trouble was protease, and using the stronger flour was the solution, is there a way I can get the best of both worlds, i.e dough that holds up its strength, but not chewy either? Said another way, is there a way to strengthen a low protein flour for use with my high hydration levain build (which is presumably what caused all the protease activity) so that dough holds up?

- I find that when I follow the instructions for Vermont SD, the dough barely rises a teensy bit when bulk fermenting (I do 2-3 folds during the 2.5 hour bulk ferment). Even when proofing, the loaf doesn't double, or even become 50-75% bigger. Most of the expansion happens during oven spring for me. Is this what others see too with Vermont SD? (I follow instructions to the letter: 2.5 hour bulk ferment at around 75 degrees, somewhere around 2 hour proofing at around 75 degrees - with poke test to ensure adequate proofing).