Hello thefrankbraun,
El Valle has it's own ISO3166-2 code and that is DO-37. You are right about the two subdivisions, they have their own codes as well. But DO-37 is the code for El Valle, so it should not be removed. DO has two levels of subdivions all caring a ISO3166-2 code. You have already been asked elsewhere (Belgium area) to start a topic at community.openstreetmap.org about your ISO3166-2 code changes. It would love to see if you do that before you continue to work on this codes and delete good information. Thank you.