I cut out a new front bodice muslin. I adjusted the front bodice piece by
-adding a side dart, then cutting it out and rotating the fullness to the shoulder gathers
-slashing the pattern from mid-shoulder to bottom through the apex and spreading 1/2 inch
-adding 2 inches of length to the entire front piece
I also pinned the front center together about an inch (to avoid my bra showing at center front). I'm not sure if this is a huge improvement, though the extra length helps. The bust apex is still too high per the mark on the pattern -- I wasn't sure how to fix this, and I'm not sure it matters given the shape of the pattern piece (note: the triangular bit on the lower right is extra paper that I didn't cut off because I laid the piece on the fold and then cut the center front apart):
The bodice still gaps out at center front rather than lying flat, and there is still gapping around the arm. What do you think?