Cool info, but I'm not sure there's enough to give you a definite answer.
The French Canadian Tessiers do have a number of descendents who became Taceys (Tessier spelled phonetically is Ta-see-a => Ta-cey).
There is another line of Taceys amongst the English/Irish clans.Ken Tacey got info from a supposed genealogist that Tacey derives from Eustache and is originally a French family that went to Ireland where it was Anglicized from the Latin.
Nowif your ancestor came straight from France to the US, it's also possible there is another name in the works.On Familyhistory.com, there are a number of WV postings on the Tacey surname page.They seem a little ambiguous.
The last interesting hook is that your ancestor came FROM France TO Louisiana, then the Middle-Atlantic region.The place and time put things in a really interesting period in French history.In the mid-1700s, the French were expelled from Acadie and dispersed throughout Canada, New England and some back to France.There was a very unsettled group that kept wandering until they found a home.Unfortunately, they started getting settled just as the French Revolution erupted.so the settled became unsettled again.Now there were no Acadien Tessiers, but there were a continuous line of ships going back and forth between Quebec and France.
One possibility is that his ancestor linked up with an Acadien wife and started making the journey with her.
But it's also possible that your ancestor was a native Frenchman who was unsettled in the Napoleonic era.It was very bloody in France between the 1790s and 1850s.If one was religious, royalist, loyalist, or upper-middle class (which is possible from his education), then his place in society would have been strained.He may not have been a Tessier, but something close in pronunciation.The entrance into Louisiana is nice, as many of those passenger lists still exist as do the ships' manifests, which give some pretty good info, including the port of embarkation, country of citizenship, sometimes even the town they reside in.
Don't know if any of this helps.But if there is anything to work with, the French Archives may be able to help (passports, passenger lists, military records, census, court records.)Also hope the Taceys at familyhistory.com can help, as there seems to be some pretty lively discussion going on and a lot of info to share.Happy hunting and good luck.