When Fiona is following Santora's guy, the guy turns off the highway and heads to one of the many islands in the Miami area.. Fi sends a text to Sam saying that the guy is heading onto Hibiscus Island. The turn the guy made actually leads to TWO islands. Palm Island first and then Hibiscus Island next.
The address, 1313 Prospect Street on Hibiscus Island does not exist, there is no Prospect Street on the island. The main roads are North and South Hibiscus Drive which are connected by numbered cross streets.
If Santora is planning to kill the snitch, why would he not kill "Detective Finlay" as well? Finlay even gives him his gun and gives him the perfect opportunity by turning his back to make a phone call.