The "American Neckline" Disaster

With my Make and Mend Challenge I had promised to reduce my fabric stash, so if I feel like sewing something, I have to address the stash. 

I've still had some interlock jersey knit in red and white and some dark blue single jersey (stretch) so I thought I'd make something. I've always liked the "American neckline" of the baby t-shirts and bodies of  the Little Misses. So I decided I'd come up with my own pattern. (No idea what that kind of neckline is called in America... or anywhere else... this is what we call it in Germany).

I used the Milchmonster Martha pattern as a base, because it fits quite well and I like it. I had to shorten the upper length and extend the shoulder seam line 1/2 inch (anyway, not just for this project).

And then I put it together like I usually do and ended up having lots of issues (see picture).

Why?

1. The interlock jersey doesn't contain Elasthan, so it stretched... and didn't go back. The Shirt ended up quite really really wide (tried to fix it, now the side stripes don't match any more...)
2. The seam underneath the bust looks really odd with the stripes.
3. The pleats from the underbust-line look really odd with stripes
4. The neckline is a complete disaster. I think the reason for this is the wrong edgeing technique. I just applied a strip of single jersey (with stretch) as usual (with the kids' shirts), but because the neckline ins curving in AND out, it went wrong. I stretched it the wrong way basically and the band is too wide for the neckline, making this problem worse. Additionally, this pulls the neckline the wrong direction (apart form standing away oddly), so I had to attach 2 (strawberry) buttons to keep it in place. 
5. When I set in the sleeves I was obviously absent-minded -> the stripes and wristbands don't match at all... (not visible on picture)

HONESTLY!!! what was I doing?? I like the shirt, but don't feel comfortable wearing it due to all the above mentionned issues.

(Will try to make a shirt like this again, though... at some point... without the underbust seam and witout the curving of the neckline)