none of us will ever get the truth Colin, but if "we" get some justice from SCA, that's enough for me.
Let OP live with his self- destructive secrets....and his family too if they are aware.
Along with Roux's thoughts I would like to know who in the family knows what. We've discussed it before but, assuming that he did knowingly kill RS, I wouldn't be surprised if his uncle and brother know the truth. Carl because of being a sibling, Uncle A because I can see him demanding to know the truth and OP not being able to lie to him convincingly. I know this makes them sound amoral, but it could also be seen as a part of Uncle A's comment about wanting to save two lives. He strikes me as the very pragmatic type and his attitude could of been that jailing Oscar for life is not going to bring Reeva back so ... Plus he seems very into maintaining the family name and reputation and a violent murderer doesn't fit well with the upstanding image.
All total speculation of course and could be total BS too but it wouldn't be the first time someone has stood by and even lied for a murderer.