I suspect that the vertical armpit wrinkle means you need less width through the chest at that point. I have fixed this by pinning out a dart on my practice version and transferring the new shape to my pattern. It can look quite odd.
You may need to add the amount removed from the front to the back, especially as you mentioned the back was pulling. Although fixing the front chest width may fix the pulling at the back as it will move the armhole forward, moving the armhole seam into the correct position.
Essentially your measurement may not be not equally distributed both front and back. Most of my measurements are different front and back.
Here’s a link to where I first came across the idea of different front and back measures,http://sewingplums.com/2011/11/26/getting-to-know-my-sizes/
Someone else may have other ideas, I look forward to hearing them.
The other thing is if it doesn’t bother you wearing it don’t worry and just enjoy wearing it, it is really beautiful 🙂