I see you wrote this post a few years ago. I came across it just now when I was doing online searches for some of my ancestors. My name's Megan Callahan and I'm also researching the Passman family who settled in Minnesota, US.
I think that DH (Daniel Hubert) Passman is the father of Annie Passman, who seems to have married Thomas Callahan, my great-great grandfather. In other words, I believe that Daniel Hubert and Maria Catharine Passman are my great-great-great grandparents.
You mentioned that the Passmans you've researched settled in Scott County, Minnesota, which matches information I have. I grew up in the Twin Cities, Minnesota as did many in my father's (Ken Callahan) family for a couple generations back, although I now live in Iowa, US.
Just thought I'd drop you a line as I was interested in anyone who might have (at least a few years ago!) been researching some of my ancestors.