You describe this as if it's common among Italian-Americans. We have several here but it seems like they are not familiar with this dish. Where did your husband grow up?
I meant, maybe a childhood friend had a relative who made this who might have the recipe.
If the recipe you tried was too sour, then maybe his grandmother used a recipe that would be considered unsafe now. Why don't you try the peperonata recipe without canning it, just to see what your husband thinks of the flavor?
Another possibility is that it's one of those things that can never be duplicated because it was his beloved grandmother who made it for him.
The trouble with eating Italian food is that five or six days later you're hungry again. ~ George Miller