Having the pattern off by one row really won't make a difference in the shoulder. A few stitches of shaping won't make all that much difference. I often don't bother with shaping the shoulders in order to do an easy 3-needle bind off.
That said, let's see if we can figure this out. Since you reverse the row you start on for the shoulder short rows, you'll start on the purl side.
After you do the first two rows, you have 5 stitches at each edge unworked. If you start with a purl row, w&t, then knit across until there are 5 left, you will have the ws facing you for the next row.
Then they want you to bind off 6 at the arm edge and work 10 more for the shoulder, right? I think what you have to do is to purl across until there are 11 stitches unworked. This will be at the right shoulder of the sweater as you wear it.
You're supposed to bind off 6 more and knit so that there are 10 stitches on the right needle. You can't do that and keep the stitches live, so you'd have to knit across until there are 16 on the right needle, turn and purl until there are 6 left.
So you have the 10 on the right needle, turn and work until there are 4 new unworked stitches, turn and work the last 6 again. Then turn and pick up all the wraps.
This is why I often avoid the shaping.