To answer the question of the packages and the package from Texas in particular: Most of the packages do not have much importance, but the one from Texas is the vital one. Our hero does not open this package but the scriptwriters' blog and notes explain that this package contained all the necessary survival items he could have used to survive, such as a water purifier, flint for making fire etc. Ironic, the meaning in life being we humans often miss the most important things we need in life because of our own bad choices.
The lady's package from Texas gets delivered to her husband in Russia at the beginning of the movie. The husband is wearing a cowboy hat and is obviously having an affair (his lover being the lady standing beside him at the door when he receives the package from his wife from Texas)... and saying "It's from my wife". So it's hinted that it was returned to sender, although there is no actual scene depicting it being sent back to the sender.
Tom Hanks' character then returns to America from Russia, does some more business, says goodbye to his wife, saying "I'll be back soon", then leaves America the second time and has the fateful plane crash with the returned package from the Texan husband on the plane with him. That part of the script is a little ambiguous and is not shown or explained properly, and is easily missed if the viewer is not watching intently. I think that part is a scriptwriters' mistake and should have had more credence in the script.
Anyhow, that particular package from the lady in Texas is now with him on the island, and hence becomes his reason to survive and return it back to Texas. Although why it is being returned back to America when the plane had already landed back in America from Russia and then left with him on the plane is the biggest mistake in the film and is often missed altogether. If you watch the beginning of the film intently, you will see that this is correct.