I don't know why this is such a hard topic. The law is pretty clear.
Sec. 9.41. PROTECTION OF ONE'S OWN PROPERTY. (a) A person in lawful possession of land or tangible, movable property is justified in using force against another when and to the degree the actor reasonably believes the force is immediately necessary to prevent or terminate the other's trespass on the land or unlawful interference with the property.
(b) A person unlawfully dispossessed of land or tangible, movable property by another is justified in using force against the other when and to the degree the actor reasonably believes the force is immediately necessary to reenter the land or recover the property if the actor uses the force immediately or in fresh pursuit after the dispossession and:
(1) the actor reasonably believes the other had no claim of right when he dispossessed the actor; or
(2) the other accomplished the dispossession by using force, threat, or fraud against the actor.
Acts 1973, 63rd Leg., p. 883, ch. 399, Sec. 1, eff. Jan. 1, 1974. Amended by Acts 1993, 73rd Leg., ch. 900, Sec. 1.01, eff. Sept. 1, 1994.
Sec. 9.42. DEADLY FORCE TO PROTECT PROPERTY. A person is justified in using deadly force against another to protect land or tangible, movable property:
(1) if he would be justified in using force against the other under Section 9.41; and
(2) when and to the degree he reasonably believes the deadly force is immediately necessary:
(A) to prevent the other's imminent commission of arson, burglary, robbery, aggravated robbery, theft during the nighttime, or criminal mischief during the nighttime; or
(B) to prevent the other who is fleeing immediately after committing burglary, robbery, aggravated robbery, or theft during the nighttime from escaping with the property; and
(3) he reasonably believes that:
(A) the land or property cannot be protected or recovered by any other means; or
(B) the use of force other than deadly force to protect or recover the land or property would expose the actor or another to a substantial risk of death or serious bodily injury.
Acts 1973, 63rd Leg., p. 883, ch. 399, Sec. 1, eff. Jan. 1, 1974. Amended by Acts 1993, 73rd Leg., ch. 900, Sec. 1.01, eff. Sept. 1, 1994.
Sec. 9.43. PROTECTION OF THIRD PERSON'S PROPERTY. A person is justified in using force or deadly force against another to protect land or tangible, movable property of a third person if, under the circumstances as he reasonably believes them to be, the actor would be justified under Section 9.41 or 9.42 in using force or deadly force to protect his own land or property and:
(1) the actor reasonably believes the unlawful interference constitutes attempted or consummated theft of or criminal mischief to the tangible, movable property; or
(2) the actor reasonably believes that:
(A) the third person has requested his protection of the land or property;
(B) he has a legal duty to protect the third person's land or property; or
(C) the third person whose land or property he uses force or deadly force to protect is the actor's spouse, parent, or child, resides with the actor, or is under the actor's care.
Acts 1973, 63rd Leg., p. 883, ch. 399, Sec. 1, eff. Jan. 1, 1974. Amended by Acts 1993, 73rd Leg., ch. 900, Sec. 1.01, eff. Sept. 1, 1994.
So you can use force to prevent the loss of property, and you can use deadly force when specific property crimes are committed (arson, burglary, robbery, aggravated robbery, theft during the nighttime, or criminal mischief during the nighttime) and there is no reasonable alternative to the use of deadly force.
There is some confusion about stealing vehicles because they are movable property, as is mentioned here, but there is a specific statute for burglary of a vehicle, and it's a class a misdemeanor whereas burglary is a felony offense.
Of course you can always use deadly force when threatened with deadly force, but that's not part of this discussion.
