Thanks so much for sharing your memories, Mary! Yes, I remember milk toast, too, but it was always warm milk poured onto toast, and given when we were sick.
When I searched "Bread Soup" online, the recipes I found seemed to use up stale bread by adding pieces to broth & veggies. It was always a savory soup, sometimes called "Peasant Bread." I'm guessing Bread Soup was just a broad term for any type of soup that included bread and it would be a good way to use up stale bread, and fill hungry tummies!
I found it interesting that someone would stitch a recipe on an apron, especially one that was no doubt, easily remembered and didn't require a recipe.