There are Johann Wilhelm Toennies and the Name FLOHR
You think your J.W. Toennies came from Jever, a place in the northwest Region of Germany
There is a Mailing list aearea JEVERhttp://list.genealogy.net/mm/listinfo/jeverland-l
I have an Reinder FLOHR, emigrated 23. Oct. 1926 with ship Karlsruhe from Bremen to New York, perhaps to Rockford, IL.
(single, 19 y.) No further Information. His bithplace was Borkum (perhaps)
So I do not believe, your ggrandparents came from Stettin, but from East Frisia or the Jever - aerea.