Well, after more examination of the Sodera sock, I became convinced that it wasn't recoverable to the point where I'd be satisified with it. There were three problems (that I could find):
1. My SSKs were messy and didn't mirror the K2Togs well at all. When I searched for a solution to this, I found that this was a common complaint, and that lots of people had gone through lots of different ways to try for a clean neat left-leaning decrease to complement the right-leaning perfection of the K2Tog. I'm doing up a stockinette swatch now to see which way may be best for me.
2. My YOs before a purl stitch were much looser than my YOs before a knit stitch. Since the YOs before purls came at the left side of the lace panel, and the YOs before knits came at the right side, I wasn't getting that nice, clean, double row of lace holes that should have been showing. It looked really lopsided. This could be fixed by being more careful and keeping my YOs at the same tension.
3. I was slipping purlwise in my sl1, k2tog, psso double decreases. This made my whole left-leaning line even more messy.
So, given all that, it wasn't really rescuable, or rescue-worthy, so I frogged it.
Whether because of these problems or not, I decided that I was no longer quite so in love with the Hedera/Sodera lace pattern, and looked more closely at the Anna socks. There are a few problems with the Anna socks that made me dismiss them before: no calf/ankle shaping at all; knit top down; only one size. But I decided those could all be dealt with one way or another, and after looking at some finished Annas, I grew to quite like the diagonal, lattice-like lace. So I cast on (top down, unfortunately) and started the lace.
And found that it was really easy, dead simple lace. YOs and K2Togs, that's all. This neatly sidesteps all my problems with the Soderas! Obviously, I will need to learn how to do all that at some point. But right now, I could crank out these socks, which are already late for my sister's birthday.