I will be interested in how others answer this question. I believe you may be more successful in finding lots rather than houses. Did you query the St. Croix Landmarks Society on this? info@stcroixlandmarks.org
Various books have reproductions of the Oxholm Map of Christiansted in 1779, but I do not know where the original resides or whether one can distinguish lot ownership from it. Did you query the Danish Archives? Much material is online at http://www.sa.dk/content/us/learning_and_research/the_danish.... There is a very learned and helpful historian at the archives, Eric Goebel, who might help. There also is a Beck map of 1754. Deeds will tell you which lots your ancestors owned and probably will describe the lot boundaries, which may give you enough specifics.