First: Ironing the toile following the grain and cross grain will restore the original form if distorted. Preshrinking is not necessary, you wonīt wash the toile, and the steam iron hardly will shrink the heavy cotton. you can check the distortion by laying on the paper pattern pieces.
Here the front was dropped 3/8" on the side seams of the back. Chest and waist lines are now horizontal on the left. On the right, not so much.
Dropping the front makes the front balance shorter relatively to the back, not longer. Where did you add length in post 256?
Just to make it clear:
when I say front balance, I mean the vertical distance between the front chest line and the crossing point of the shoulder seam and the neckhole.
When I say back balance I mean the vertical distance between the back chest line and the crossing point of the shoulder seam and the neck hole.
Maybe your back balance is longer than before because you mixed up sewing line and sewing allowance line? please compare this measurement in toile and pattern.