Shirley,
This is what I found. Nothing more in Vols. 1,2,3 but in Vol. 4 I found:
1. Eustache Bueche married Clemence Gueho 9 Apr. 1822 (Vol 4, pg 108).

2. Eustache Bueche ( Eustache and Constance David) civil marriage, born 1 Sept. 1837 bt. 15 Oct. 1838 sponsors were: Jean Baptiste Prospere and Clara Bueche, his sister (PCP - 4, 203) DBR Vol. 5, pg 126.

3. Eustache Bueche, age about 50 yrs., buried 14 Nov. 1845 died yesterday (PCP - 11, 27) DBR Vol 5, pg 126.

4. Touissaint (Eustache Bueche and Constance David, civil marriage) bn 12 May 1841 bt. 24 June 1841 sponsors were: Olerien Bonaventure and Helene Guihot (PCP -4, pg 252) DBR vol 6, pg 129)

5. Eustache Bueche ( parents not given m. 25 Aug 1857 Eulalie Lejuene (parents not given) witnesses: Octave Chustz; Uranus Sicard; Jno A. Sicard (PCP - 8, 338) DBR vol. 8, pg. 119.

6. Pierre, age 23 yrs (Eustache Bueche and Clemence Gueot, both deceased) Husband of Perinne David buried 3 June 1856 (PCP - 11, 154) DBR vol 8, pg 119.

I still have some more books to look in and I'll send the info as soon as I find it. Also, I know these entries are not answering your questions but might steer you to new leads.