Since your quilt top is so fragile and not quilted yet, I would secure the gaps caused by large stitches and quilt the top by hand or have it quilted by hand. It doesn't sound like the top could survive the rigors of machine quilting. Once the quilt is quilted and bound, then I would address the stains. I would discourage you from using anything stronger than a little lemon juice and some gentle soap intended for quilts. I would soak the quilt and gently launder it by hand. Remember to rinse again and again. I would use a color catcher sheet in the wash water and rinse water. Do not wring or twist the quilt; rather, gently roll it in towels and spread it out flat to dry indoors. The wind could damage the raw edges of your top if put outdoors to dry. If the stains come out, wonderful; if not, you would still have your great-grandmother's quilt. I have had a good deal of luck washing quilts with Orvus, a low-sudsing, gentle soap that's often for sale in quilt shops. Orvus is also used for washing race and show horses, so I buy mine at my local MFA feed store. It's much less expensive this way and it's the very same product. best wishes....Barb