I had to figure out that the counts for the armhole decrease total stitches per row did not include the stitches that I had to increase for the cable design. I think that's part of what confused me. Once I figured that I had an extra 24 stitches because of those increases, it worked out just fine. I'm about 3" short of having the back done
At some point I'll figure out what stitches are best to use for seaming, but I think I have a week or two before I have to figure that out.