Loss of Sabine would have brought about an earlier collapse would it?
It's very likely. Had Sabine been lost, the invasion force would have landed and probably advanced across Texas by 1864. It would have fallen by Lee's surrender instead of surrendering on its own several months later. The south would have also been deprived of blockade runners after Mobile fell in 1864. The north would also have never needed the Red River campaign, which diverted many troops and ships away from the war elsewhere. So in effect, a 40 man garrison at an earthen fort significantly altered the time and course of the war.