Looking for records of my great-grandparents

I'm looking for records of my great-grandfathers on one side. (Grandmothers would be nice, but heck, I barely know their *names*)

Great-grandfather number one, Jacob Dannhauser, was born in 1922 in Buchau, Germany. (I'm not sure if it was called Buchau then; probably some permutation thereof). He was Jewish ("Hebrew") which probably would have been listed in naturalization things. He arrived in the US in 1938 or 39, and moved to Cleveland. Many of the family records have been digitized, but I've been unable to find his. (See, e.g., https://catalog.archives.gov/id/147837194 for Siegfried, his father; https://catalog.archives.gov/id/147837201 for his mother; and https://catalog.archives.gov/id/147861565 for his sister). He also served in the army, so there might be records there. I'm looking for almost anything; naturalization, census stuff, army records, et cetera.

The other great-grandfather on that side, also named Jacob (life is confusing), lived in New York City with his wife Frida/Frieda/Freda (I don't know which) and died in the fifties. He had two kids and worked somewhere in law, I think as a clerk; he was fairly young, I believe (because one of his kids was also pretty young; he was eight or something). Again, almost anything.