Although this is a nonAEA show or house, there must be someplace clearly written out the responsibilties of the SM - and if they need help, go to the AEA website and download from, oh, let's say the LORT contract the definition of the Stage Manager's job description.
And, if I may humbly suggest, part of standing up for yourself is, instead of saying that you suggest someone else does the laundry and explaining clearly and rationally why it makes no sense, you rather say "NO, that is not part of my job, and this needs to be done by a wardrobe person or other member of the costume dept." Period. And as a follow-up, if they want still you to do laundry, they need to compensate you appropriately for your time. Say, for example, a figure equal to the income from your day job which you will need to miss doing their extracurricular tasks.
If they can't pay you a full-time salary, they cannot expect you to work there full-time. And under any conditions, you should not be responsible for personally taking care of jobs outside your arena.
Good luck....