PatH, true, we cannot really answer the questions yet, merely speculate and, possibly, withhold premature conclusions.
To backtrack for a moment : Mrs. Feathers went to the clinic by boat, the only conveyance to the Port, accompanied by Ada's (unnamed) mother and her own baby to be wet nurse for the new baby. The poor woman was frightened to be away from her home, and Mrs. Feathers comforted her.
Ada was 12 years old and the eldest daughter of the wet nurse. She had seen her mother off and was at the dock when her mother returned.
The baby's father was not. Ada, not yet a teenager, was put in charge of Edward and he became a part of Ada's family.
He grew up with the brown Malay children and, of course, learned Malay. In the village were "a number of pale-skinned half-caste children from the Raj's peccadilloes" but Edward was the fairest with blue eyes and his mother's curly chestnut hair.
He was 4 1/2 years old when Auntie May returned. She had been in correspondence with Captain Feathers and came back to discuss Edward's future - in England. That was Auntie May's job and, besides, the only reasonable solution for a motherless white child in the Far East. A dinner was arranged at Captain Feathers' home, the child summoned and, holding Ada's hand, waited outside until called in. In Malay, Alistair tells Edward that he is his father (the childdoes nott believe him), that he is to return Home ("why can't I stay here?"), to learn English first ("I can talk here ... I would like to stay here ... I should like to die here... Will Ada come").
The plans are finalized, first a foster home in Wales, then boarding school, and more, prepaid by the father and held in trust. Told by Auntie May that "Your sisters must organize warm clothing for Liverool", Alistair replies, "They wouldn't know how. They're independent spinsters.
Play a lo of golf." The Kotakinakulu chapter is sad but worth rereading.
Long separations between parents and children, or any abandonment, are known to have deleterious effects on the victims, and Edward surely was one.