A target of 250 is more than enough. Surprised with you mentioning Peterson and Bavuma. I consider them as the weakest part of the South African batting lineup. For South Africa, if their top batsmen such as Dean Elgar, Aiden Markram and Rassie van der Dussen fail to perform in the second innings, then the chances of a win becomes close to zero. Keegan Petersen have been exceptional so far in this series despite his lack of experience. But I don't think that I can say the same about Temba Bavuma. He has played a few useful knocks. But that's all.
250 plus will not be an easy target for South Africa. I am not sure how long Pujara will stay in the pitch but hoping Kohli to stay their longer. Still a lot of batting left and I think they will easily add 200 more runs to the existing lead of 70 runs.