Clark has started to speak to Lois.
I am not sure his staying indefinately with the Bangala will work, in some ways it seems to much a victory for Tempus. Still, he will need to stay here a while to even begin to heal.
Lois is a very good therapist for him. This will be a long process of healing though.
I still interpret "teach him English" as the process of teaching him writing as well as speaking. Anyway, children have to be taught to speak, especially if it is not the common language of a place. At least I see nothing in that phrase to indicate that Diddi is not Lois' natural child.