After the author retired, why did Sai Baba insist that his pension was insufficient and that he needed to find a new job immediately?

This is a misunderstanding of the events described in Chapter 3. Sai Baba did not insist that the author's pension was insufficient. In fact, it was another devotee, Anna Chinchonikar, who voiced this concern on Guru Purnima in 1916. Anna pleaded with Baba, saying, "In his growing household, please show grace upon him. Find him another job; will this pension be enough?" Sai Baba's response was one of reassurance, not agreement with Anna's worry. Baba stated that the author should perform His service and that by doing so, "His plates are always full; they will never be empty as long as he lives." Baba's focus was on spiritual service leading to worldly well-being, rather than the insufficiency of the pension.