The grandson of Ambroise, Jacques Fauchon, has location information for marriage and death, which might be sourced. Careful, though, a great part of archives in Manche had been destroyed during WWII battles (stumbled on that problem for some of my wife's maternal line).
[edit] : just checked for Chalandrey, marriage place of Jacques Fauchon : archives start in 1802.
The place seems to be Vézins, not Isigny-le-Buat (into which it was merged in 1973, so the registers of Vézins are kept in the town hall of Isigny-le-Buat, but they were distinct parishes).
Archives for Vézins start in 1700. Here (bottom left) is the record for the marriage of Magdelaine Fauchon, granddaughter of Ambroise Louvel. She is said to be "de cette paroisse", and indeed the Fauchon family is well present there.
I think the source of these profiles is an undated manuscript, probably from the late 1960's, kept at Archives départementales de la Manche : "1 Mi 493 : Histoire généalogique et anecdotique des Fauchon sieurs de Villeplée, de la Margueraye, de la Haute-Folie depuis les années 1400 par le général Jacques Fauchon de Villeplée (378 vues, octobre 2021)".
For instance, it contains a partial transcription of the marriage contract of Julien Fauchon and Ambroise Louvel, on 24 Apr 1660 before the tabellions of Chalandrey.
