the town you're looking for should be Saarbrücken, which is right next to French boarder in South/west Germany. Couldn't find any "Kleinwald" there though, neither village nor region. However did find "Kleinwalddorf" which is near Kelheim, about 7 miles from river Donau, next bigger city would be Regensburg/Donau(Danube). People from there would very likely say that they are from Kleinwald cause the original name is rather long and means a small village in the woods. Hope this is of some help for your research.
My husband's grandma was married to Ernst RISTAU (her second marriage), his place of birth is unknown, but this couple emigrated to Argentina in the early 1920ies, where some of the Ristau descendants are still living today.