Was Kashiram under a vow to give Sai Baba Dakshina every single day?

No, the text does not state that Kashiram took a vow to give Dakshina daily. It does specify that Kashiram took a formal vow to provide Maharaj with other items, namely "chillum and tobacco, and firewood for his Dhuni, and money if needed" (Chapter 0). While he was not under a vow for Dakshina, he did become extremely eager for Maharaj to accept it from him each day, and he would feel very bad if it was not taken. This strong personal desire, which led to pride, was what Sai Baba later addressed to help Kashiram's spiritual progress, but it was separate from his actual vows.