I realize your post is several years old, but I just read it today. Your grandfather's father was indeed Joseph Henry "Joe" Alexander. His wife was [Margaret] Janette "Nettie" Fields. The Weimer cemetery you visited is full of your family! One of Joe's brothers was Ora Alexander, who was my great-grandfather. He died when I was 5, but his wife I remember rather well.
I have LOTS of info on this Alexander family. Wanna talk?
Jennifer Rice / firstname.lastname@example.org