Ok, so many mods…but really easy to follow and or modify.

First of all, I want to knit somewhere between an 8-10, and I normally get 18sts/4” with this needle/yarn combo…so I cast on the stitch count for the 10. Lengths taken from size 8, but modified…

Next, as others have said, the body is very short as written. Lengthened to ~11-11.5” before arm holes. (64 rows total)

Sleeves worked in the round, as for size 10, to 61 rounds before joining. Worked 1 row less than written for cuff sts, to match bottom edge of body.

On last row(WS), before joining sleeves, bind off underarms. Do not break yarn.

Buttonholes, I made 3, on the 1st 3rd and 5th eyelet rows.