Once you put the stitches on the holder, they stay there until you're ready to work that side of the V neck. Work the stitches that are still on the needle for the 3 rows.
Then bind off for the underarm only on the underarm edge--not on both edges, since one edge is now the neck.
After you complete the one side, you're done with that half of the front. Put the stitches from the holder onto your needles and work the raglan decreases as you did on the other side of the back, and work the V decreases at the neck edge.
Once you get going, it'll be easy to reverse the shaping, since you have a neck edge and an armhole edge to refer to.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog