"The collar is also not straight" I had to laugh... Up today I have sewn two sweater, and both are... how should I call it... creative? I found it so hard to make the neckline. Mine is not only also not straight is furthermore so wide I unknowingly made an off-the-shoulder sweater. And it doesn’t lay flat… sigh.
You did a great job, the little irregularity you mentioned are not important. I am so curios to see how you will make the upcycling project! I am pondering to make a sweater from my 'skirt scraps' but after my failed attempt I am intimidated. (I used a book for pattern making with jersey fabric. It is called 'sewing without pattern' but in reality you learn to make the pattern yourself.)