Ironsoul, the "welding vertices" seems to have worked. Thank you!

Daffy34, in Sim Settings I had checked Cloth Self-Collision, and in Collide Against I added M4 and checked Ignore Head, Hands, and Feet. (I'm assuming it knows the difference between feet and shins.) The folds are still a bit crunchy, so there's still some work to do in the higher settings. I thought self-collision would take care of that, but it doesn't.

I think I can skip the Soft Décor option for this part now, but is that what I would use for the stitches?

Thank you!