Worked a bit more on the code. It now sets the appropriate horizontal size and aspect ratio, and I tuned it to actually have the appropriate line length to keep the orientation straight.
It still doesn't find the sync pulse yet, but it will soon. Interestingly enough, the sound card is accurate to less than one sample in 11025, the difference between the nominal sample rate and the one that produces straight vertical lines is less than one half a sample per second. I find that pretty amazing.
Addendum: I mentioned yesterday that i was getting a much better signal from Australia than from Point Reyes. Here's an example of images that I'm getting from Pt. Reyes.