I also read your post on the Osborne Family Genealogy Forum. When I saw your father's birthdate I wanted to pass along an idea that should help. The 1930 Census is now available. He would be five years old and it would show parents, siblings if any and a great deal of information.
I don't know where you live but check in the telephone directory for The Church of Jesus Christ of Latter-Day Saints. They may very well have a Family History Center. You can go there and order the microfilm you will need. The only charge is the rental of the film. Usually they will keep the film in their library for several weeks. Of course if you live in DC you could go to the National Archives and read the film at that time.
Do you know if he was brought back to the states for burial? I looked in the ABMC and the two Floyd Osborne's listed died before 1945.
Good luck. I hope this helps. I would like to know how it turns out.