Thank you for taking the time to write all of this down.
Some time ago, I believe I did find on a record from Norup a marriage that probably included Johann's birthplace. I read Danish, but this one was very difficult to decipher.
I also found a Johann Denhardt (multiple spellings which appears to have originated from Steinrode, Germany, a bit northeast of Frankfurt.
There is much more research to be done here, but I am optimistic that this one will be solved.