After mucking around (and frankly, struggling monumentally) with wet, sloppy dough and basically just not cutting it with > 70% hydration sours, I took a plunge with @jaxler12’s recommended method along with a different (albeit pricier) brand of flour. The dough was delightfully manageable and it lent itself to (finally!) being properly shaped, all leading up to great oven spring, that elusive ear (or Mohawk?) and the lightest, airiest, deliciously tender crumb.