The above suggestions and observations are good. If I may add a couple of small things, when looking in The Netherlands for "John" one should try "Jan" and for "Doras" one might consider Dorus, as in Theodorus. A good example is that the famous Dorus Rijkers was in fact Theodorus. (His brother married a cousin of mine.) Also, while "Stockton" is not to be found in NL, there are two towns named Stokkum, one called Stokhem, Belgium has one named Stokkem, and Germany has two named Stockum. Census takers are notorious for misunderstanding what someone tells them and frequently write things down wrong.