I'm going to show how I can reverse those cables I crossed the wrong way. As far as I know, there are two ways to do it. Luckily, my old swatch for the sweater has two repeats in it. They are knit with two different sizes of needles, of course, (that was the point at the time) but the difference in gauge doesn't matter. Here's the correct swatch, with both cables crossed to the left.
For the top cable, I cut the top stitches and moved them to underneath. This was very scary, since I had two tiny short ends to secure. The result is flawless from the right side. It really looks like a correctly crossed cable. However, from the wrong side, it doesn't look so nice. First, there's the two ends, which I knotted together, sticking out. Second, there's a bit of sewing to secure the loops of the stitches I cut and to close the hole. I'm worried the hole might reopen with wear.
I'm not aware of any other methods of correcting the problem, short of reknitting the sweater. Unless I find a better way, I'll probably use duplicate stitch.To sunset this issue, here's a photo I took in Wyoming en route to Yellowstone.