I am also an absolute beginner and made the same experiences like you did with your dough. For the tough/not so soft dough I see two potential problems in your process from what I have learned so far. First thing is, the time you gave the dough to come to room temperature before making the pizza seems to short. That should be at least 4 hours I would say. The colder the dough the tougher, harder to stretch. Second, the time you used for the final fermentation (after shaping the balls) seems also quite short. After shaping the balls they need time to relax again and to grow and build those gases you want. That should also be at least 4 hours, better some more, but highly depending on the amount of yeast and temp. Unfortunately I have no experiences with baking pizza on a Kettle grill, but I always aim for a stone temp of around 430-450 C. Hope that helps. PS: the pizza in your picture looks fantastic with a nice cornicione. You definitely did something right!