I am having a problem with moth ball odor in an antique dresser, so saw your request for help with your sweater.
We live on a farm, and when my son was in grade school. he went to a neighbor's farm with his Dad wearing his new Reeboks, three days before school was to start. To make a long story short, he got into a pen full of hog manure "slurry" and fell down in it. I called Iowa State University Extension to ask if his clothes and shoes could be saved. They recomended washing both the clothes and shoes in the washer with white vinegar and then setting them out in the sun for several days. I was totally surprised when it worked and my son was able to wear his new shoes to school. Hope the white vinegar will work on your sweater. Don't know if it will take just washing in the white vinegar or also hanging in the sun. Good luck.
Note: the white vinegar wash has worked in removing other odors also.