*I have 14 sts at the beginning of these instructions
Row 4(WS): With Yarn A, p across
Row 5: Bind off 1 (2,2) for neck, K to end
Row 6: Bind off 5 (7,9) for shoulder, p to end
Row 7: Bind off 1 (1,2) for neck, k to end
Row 8: Bind off 4 (6,8) for shoulder, p to end
To reverse the shaping you need to begin the shaping either on row 4 or row 6. Let's do it on row 4:
Row 4 you are on the wrong side and you bind off one at the neck edge (like row 5) and purl to the end.
Row 5: RS bind off 5 for the shoulder, knit to the end.
Row 6: Bind off 1 at the neck edge, purl to the end.
Row 7: Bind off 4 for the shoulder, p to the end.
As you found out, you can't bind off 4 or 5 at the end of a row, so in reverse shapings you do the BO on the other side from what you did them in the first place. It makes one front 1 row longer than the other, but that doesn't show when you are done. You can bind off 1 stitch on the right side at the end of a row, but I would just work two stitches together myself instead of using a BO in this instance.