Hydrogen peroxide is very hard on fabric. I would try Z'out (inexpensive spray stain remover at Walmart). Years ago it successfully removed dried blood from a dress that would have been ruined otherwise. You could also try soaking in OxyClean. There is a soaking treatment that is made specifically for vintage items, but I can't remember the name offhand.
Here is a link to how hydrogen peroxide affected one of Leah Day's show quilts (scroll down to see end result):
https://leahday.com/pages/duchess-wholecloth