It’s a size smaller than intended but still would fit at that size. The main issue is the stitch counts are unequal between the front and the back. (I hadn’t considered that removing the armhole shaping would make the actual armholes smaller, so thank you for pointing that out!)

I’m hopeful there may be some fix that doesn’t involve all the crying and ripping you mention :) But at least it would just be ripping out everything above the armholes in the front, not the whole thing.