There are no church or civil records available for Jeremie for the period you are inquiring about. The only available ones are the parish church records from 1778 to 1790. The only other sources in which you might be able to find some information relating tothe Simon family of Jeremie are the minutes of the notaries for the parishes of Jeremie, Dame Marie and Cape Tiburon. The last two contain a surprising wealth of information on Jeremian families.
In fact, Guillaume Simon was an habitant of Jeremie. He owned a coffee plantation in the district (or Canton) of Grande Riviere de la Grande Anse. I found his name in a document relating to the purchase a property by a local habitant, in which references to adjacent property owners were made, in order to provide an accurate description of the exact location of the land. He was one of them. No more is known of Sieur simon.
However, during that same period, there was an Antoine Julien Simon, a "metis" who was known as a wealthy habitant of the same district and whose father was a European colonist. He might have been a natural son of Guillaume Simon. He was married to Catherine Estival, another "metis". They were parents to a number of children including three sons, Julien, Etienne and Antoine. The elder was to become the ancestor of a present day Haitian family.