I was like you for a long time, especially since at the time I had a round Dutch oven. But, since getting batard bannetons as well I've loved the taller loaves I get with more loft to them.
Great blisters! I think the trick to keep in your head is that fermentation curve.
As usual, lovely breads.
Pretty sure that you were weighing for your normal breads (how else would you make, say the Tartine country loaf)?
It makes sense to weigh the starter amount as well then, just to make things repeatable.
Yes, you can!
Simply use some to start an off shoot (which will become the levain for your bake). Most starters adapt well to all kinds of flour, but do tend to do better on whole grain, so something like whole wheat is a good place to start.