How did travis and other texans at the alamo improve their situation?

They got the women and children out so that their protection was no longer a factor that could detract from their energies. They drew a line in the sand offering to let any leave that wanted to, knowing that all who remained were not concerned of their own hides, but only of efficiently killing as many of the enemy as possible. Thus, those that remained knew they were going to die and could focus on staying organized, selflessly helping the rest of the army to final victory at San Jacinto. They did all they could. They were also able to vindicate Fannin's men, who were ruthlessly executed after surrendering at Goliad. This showed Santa Anna that from now on there would be no more surrender, but a unanimous resolve to fight to the death for their country, Texas. This improved the Texan's situation by weakening the enemy as much as possible, showing their resolve to fight to the death to defend their homes and families, making Santa Anna face the reality of the greater risk of an offensive war away from home.