This trial is about him. Of course his testimony is going to be about him and his actions and his beliefs and perceptions. That's why we're having this trial. It's not a memorial or tribute to Reeva; there's going to be no evidence about whether Reeva deserved to die because everyone agrees she didn't!
No, but she does deserve to have the right verdict brought against him .. and if she did in fact die in a DV incident, then it would be an absolute travesty for her and her memory, and her family and friends, if it just goes down that he killed her by accident. That's why the absolute truth must be reached .. for her .. couldn't care less about him (but if the truth is found for her, then it follows that he will receive the correct sentence according to that truth, so you needn't worry about that).