I'm glad to hear it was a fruitful lead! (I've had a few records of divorced and widowed women give me the slip, too.) I took another quick spin on Family Search for Whitmer siblings, and like Orla's 1930 census, some records say their father was born in Germany, which opens up a can of worms for Phillip Whitmer. (Did he lie about his birthplace because of cycles of anti-German sentiment in the US? Were his children mistaken about his birthplace? Did he grow up speaking German because his parents were immigrants, and people around him made assumptions?)
Ha! In case you can't tell, I'm excited for you :)