Are there other accounts in Chapter 33 of scorpion stings being healed by Sai Baba's grace?

Yes, in addition to the story of Narayanrao's friend, a footnote in Chapter 33 mentions two other instances of scorpion stings being miraculously healed. One account is of Bapusaheb Jog, who was stung and went to Baba. As he climbed the steps, Baba simply said, "It will be alright, go!" and the pain stopped completely before he even left the compound. Another story involves a Jyotishi Buwa who was stung in Rahata. He applied Udi given by Baba and continuously chanted his name, which stopped the severe pain and firmly established his faith in Maharaj.