The good principle shall continue forever, but the evil shall cease to exist after Ragnarok. Vidolf, Vilmeide and Svarthofde are mentioned nowhere else in the mythology. The idea then is that Bor united himself with that which was best of the miserable material at hand. That the flood caused by the slaying of Ymer reminds us of Noah and his ark, and of the Greek flood, needs only to be suggested. While the etymology of the name in the myths are very obscure, the myths themselves are clear enough.
Similar myths abound in Greek mythology.
The story about Bil and Hjuke is our old English rhyme about Jack and Gill, who went up the hill to fetch a pail of water. In reference to the golden age, see Norse Mythology, pp. 182 and 197. While the giants are always hostile to the gods, the dwarfs are usually friendly to them. Both giants and dwarfs shun the light.