Since we last corresponded I have continued researching the Chavana name in the US Southeast and in Mexico's Northeast - I am from Monterrey. I now have a file of over 150 Chavana from the 1700s to late 1800s.
With the help of a Chavana cousin scouring the regional archives in Monterrey and history books, there is evidence that Miguel Chauvin/Chauvain (my ancestor) is the origin of the name Chavana! His surname in Spanish sounds like "shavan/sssaban". He is recorded as Miguel Saban in various places; some of his first children were registered as Saban and the latter children as Chavana. (Later on there are individuals who were recorded as Chavana in one record and Chabana in the next record; thus there cannot be a hard distinction between these two surnames.)
Miguel shows up in a history book (...Apellidos de Tamaulipas, Nuevo Leon y Coahuila...) as having having been born in 1719, in Limorsin, France - Son of D. Diego Chauvain and Juana Novada. (Probably translations of french names.) In 1735 he came to New Orleans as a french soldier (said to have deserted) and settled in Lampazos, Nuevo Leon, Mexico. The book goes on to describe marriage dates with Catharina de Leon, ganddaughter of Fernando de Leon - a Spanish Explorer who made several expeditions to Louisiana (presumably to colonize and/or ward against the French). Also included are names, dates and mates of several of his children.
One of Miguel's children was Jos. Ramon Chavana (born in Lampazos) and has about the same birth year (1764-1766) as a Ramon Chavana who has a GED file (at ancestry.com, I believe) as having been born in Lampazos and married (Jofefa Sanchez b: 1784, Nacogdoches, TX); their 13 children were born in Nacogdoches and in Natchitoches, LA.
While travel was not easy in those days, especially with Indian raids, it is interesting to note that the Camino Real from Mexico City to New Mexico passed through Monclova. From Monclova, ver close to Lampazos, there was a branch of the Camino Real that went to Natchitoches, LA.
Regarding names of your ancestors, I have a cluster of 5 individuals but I no data on how to connect them with anyone else. Perhaps you may recognize them and we'll make a connection. Vincent Chavana (b:1812 in Mobile, AL) first married Catherine Dubroca (on Jan, 8, 1839 in Mobile) and had a son Hugo Chavana (b: Feb 15, 1842 in Mobile). Hugo then married Soledia (Soledad?) Gomez (on Nov 18, 1868 in Mobile). Vincent's second wife was Mary Maydalena Pollard (married on April 10, 1863 in Mobile).
I hope that in the meantime you have also encountered more names and perhaps we can find common data points.