Interesting thought -- it never occurred to me before that TA had actually deleted the tryst pictures, but you're right, it would just add to her rage. I, too, feel that she drove to that house with the intention to win TA back, and kill him if she couldn't.
I'm not sure that TA was afraid of her, physically -- I see him more as simply a red-blooded young guy who was struggling with trying to adhere to the dictates of his faith, and was at a weak moment, having just been rebuffed by the woman he'd thought might be "the one," who was now just going to Cancun with him "as a friend." (While I'm not Mormon, I come from a similarly-conservative Christian background, and am well aware of the cycle of guilt that young Christians feel when engaging in various sexual activities, as well as the rationalizations, e.g., "oral sex isn't real sex, so it's OK," or "anal sex isn't real sex, so it's OK" they often use to convince themselves that they're "still a virgin." Much of what JA said about Travis's communications to her in that regard is very familiar to me -- I don't see TA as trying to fool JA into impermissible sexual activity by telling her that certain activities were OK; rather, I see him trying to protect both of them from guilt, as well as to find a way to rationalize their sexual antics so they can keep on doing them, for their mutual pleasure.)
While he had recently re-committed to being chaste, Jodi caught him at a moment when his defenses were down, and was able to talk him into one last sexual romp, which I am sure he had come to regret even before those final shower photos were taken. To me, the discomfort he shows in the photos is caused by guilt at what he is doing, rather than fear. I think that at some point between the sexual activity and the shower, they had a long talk, and he tried to make her understand that pigtails and Brazilians weren't going to change his mind about the fact that their relationship was over.
I wonder -- did the photo expert say anything, or have any information, about WHEN the photos were deleted? Is it possible to know whether TA could have deleted one batch before the shower pics, with JA deleting the rest after the murder? Interesting stuff.