Imperfect Fit on the Perfect Dress

I'm making a test run of the potentially perfect dress, McCall's 5753, in a chino fabric, which I cut it out in my usual size 12 (34 bust).  The neckline is a lovely shape - wonderfully dipped, but not too low. The skirt pockets took a few tries, but are a great feature.  I got the zipper in, slipped it on for a full-dress fit test, turned around to peep at the back and saw this:

OMG?!  WTF?!  Why is the bodice ridonculously wrinkly and baggy?  And the right more than the left? 

I couldn't tell from looking in the mirror what the problem is, but I think it is clear in these pictures that the bodice is way too big.  This is so strange, because a size 12 generally fits me well.

At first I believed the front bodice fit, but it too may be big, as the top is gaping:

 

I cropped out the full decolletage shot, as it is rather scandalous!  The Captain is lurking in the background.

Conversely, I may have a bit of a "large buttocks" issue.  Referring to my newly purchased  "Fitting & Pattern Alteration: A Multi-Method Approach" reference book, the pulling going on here:

Is awfully similiar to that in the picture.  However, the behind area doesn't feel tight; instead, it almost seems as though the lines are due to too much fabric above the behind to the waist.  Has anyone experienced this before?

I believe my new book, which was recommended last year on Miss Celie's Pants, will be really helpful in solving challenging fitting issues.  But I wonder if this fitting issue is even more basic: should I simply go down a size in the bodice?  Even then, I question whether the bodice will be small enough, because it seems very big.  Perhaps I need to shorten the bodice itself?  I do believe that I have a shorter torso than most. 

I'd love to hear your thoughts on this!