I do not understand why a second fabric or stabilizer is added to the backside of an embroidery piece. I’ve read it’s so that thread travels doesn’t show through - but for you are embroidering correctly, you shouldn’t have any threads showing from traveling from one area to another. And about your muslin being wrinkly - regular starch should take care of that if it a quality muslin. I really like “Kona” fabric from Robert Kaufman as an embroidery background. And I do not prewash it. I’ve never had any problems with thread bleed as I sort of wash it afterwards. I’ve been embroidering since 1965 so I do have a little experience����