Pretty sure it would be Wallerawang, originally called Waller-owang by the native Wiradjuri people; and later Charles Darwin used the spelling Wallerowang. And as Neale1961 has found in his first reference, the town is about 100 miles west of Sydney. Neale’s second reference is to a property name, so probably just a coincidence (unless the property was named after a spoken reference to the district or for the aboriginal meaning of the word, ‘place near wood and water, or plenty of water’; the marriage certificate says Wallerong, NSW so I think it would be referring to a town or district, not a property.
Peter