The Castle Doctrine in Texas was successfully stress tested in court a month after it was passed in 2007. It applies to your vehicle also.
The interesting permission that Texas law gives is in the case of “robbery” in addition to “aggravated robbery”. This goes against the USSC ruling in the case where a farmer set up a trap to kill anyone robbing his abandoned house, http://en.wikipedia.org/wiki/Katko_v._Briney. If you have some references on Texas’s ruling on “robbery”, again I’m interested.