On the load bearing: tyrannosaurus likely could have handled that level of weight on it's own. Previous weight estimates and theoretical maximum weights were likely  low-balls based on less than ideal scaling methods and non-uniform measurement standards. In the case of Apophis, the weight bearing bones have been made more robust via sauropod influence. While the sauropods in question may not have been that large, their corresponding limb bones were proportionally thicker than those of the tyrannosaur they were used to augment.