Apparently these socks are just not going to happen. First, I cast on 72 sts, the correct size, but I did not like the pooling.
So I tried it on, pinched the sock down to 64 sts (the next size down), found that 64 sts would work around my ankle, and restarted the sock. I'm LOVING the spiraling, the fabric, and pretty much everything about this sock, except one small detail.
64 sts might fit around my ankle, but the sock can't get around my stupidly-shaped instep. Bah. I have no idea what will become of this yarn, but it won't be socks!