1. Can I edit it? Add more details? Change the category so its a tattoo/blush/mole?
Go ahead! Edit this all you want. Just give credit if you reupload. I made this for myself and I really only upload the file that I made as an afterthought.
2. Ewwww.
It's a strange overlay, isn't it? I'm not supporting eating disorders or glamorizing them. One of my sims has a backstory that as a result left him quite frail and this is to detail his condition.
3. Why not include preview pics of the middle skin overlay?
It's legit just the same thing only like a tad lighter. The third one is the same only it doesn't include the spinal overlay.
4. You got permission?
Moonskin93 has a very lax TOU that you can read here.