Finished! After a little over a month of working on them, I finished the mystery socks. Working on 2 circs, I worked them both at the same time. It's very satisfying to pull them off the needles at the same time. And though it might take slightly longer to complete them, they still knit up much faster than if I worked them one at a time.
I used the Zimmerman sewn bind off for the first time as well, and it is definitely my favorite cast off for toe up socks. I knitted up Cat Bordhi's Leaf and Tendril socks right before starting these socks, and the cast off for those is interesting but I don't like the look of it as much. The sewn bind off looks much cleaner.