I’m still team all-piano as I got more of the feeling that Obi wan was experiencing horror for what Anakin has become more than fear for his own safety. Obi doesn’t seem to hold himself in high regard at the moment so I didn’t feel that he was that scared of dying in the moment, and was more experiencing fear in the sense of fearing the reality of who Vader is and what he has done. It a fear of the truth rather than a fear of “I’m scared he is about to hurt me”. Seeing the kid be murdered didn’t cause Obi to flee in fear because he was scared that that was about to happen to him to, he stared in shock because he feared the truth of his failure to Anakin. This type of fear greatly changes how the scene should be scored, but of course this is all open to personal interpretation. I would say he “feared the sadness” which is why I thought the piano theme is most fitting.