What are your sources and references for stating that Michael Burkhalter (1720-1804) was married twice? He was already married to Anna Denzler by May 1745 and she was the wife named in the will of 1807. In his will, Michael named 6 living children and 2 grandsons through a deceased daughter. He did not have a son Christian.
It is incorrect that Michael Burkhalter (1694-1762) was married to Barbara Walthaur. That marriage took place in Switzerland in 1703, when Michael was a youngster. There were 5 Michael Burkhalters in the same parish in Switzerland, so they are easily confused.
Please see my posting at Ancestry.com or Rootweb.com for several early generations of this family. Also I have posted information about Michael Burkhalter (1720-1807) at this Burkhalter surname page, message #503.