I think I found pretty much what you already have.I do think that Gilbert was indeed Gus's father.All census data seems to prove that to be the case.
I'll send what I came up with anyways...
1850only one fits: Gustave Lacour Not Stated, Liberty, TX abt 1846 Louisiana household: Gilbert 32Merchant LA Aurilia 32w LA Palcherie 9 (female; index shows Pulcherii) Gustave 4 Oscar 2
also in this county is: Ellen Lacour Not Stated, Liberty, TX abt 1795 Louisiana Gilbert Lacour Not Stated, Liberty, TX abt 1792 Louisiana
1840 Gilbert Lacour Not Stated, Rapides, Louisiana
1860 only one result (surname soundexed) Gustavus Laccore Precinct 1, Jefferson, TX 13abt 1847LouisianaMale household: Gilbert Laccore 41 Orvilla Laccore 42 Gustavus Laccore 13 Oscah Laccore 11 Gilbert Laccore 3
1870 Gilbert Lacour Ward 10, Natchitoches, LA abt 1819LouisianaMulattoMale (image shows a M?, rest of the family show W, I think Gilbert's supposed to be a W/White too) Gilbert 51Farmer Orelia 51 Gustavus 22 Oscar 20 Joseph G 13