The "FULL_STREE" Just a column name of database to show information to user.
I am not sure how you create and use the index file(".rtg"). Please try following steps.
1. Create routing index file from “.sqlite” using Routing Index Generator, the "Geography Unit" must be the same as geography unit of “.sqlite”.
2. Use SqliteFeatureLayer to load features from “.sqlite” file as following.
routingFeatureLayer = new SqliteFeatureLayer(connectionString, "osm_road5m_linestring", "id", "geometry");
3. Set the GeographyUnit of RoutingEngine following the same Geography Unit of “.rtg” (look the attached above) as following:
RoutingEngine routingEngine = new RoutingEngine(new RtgRoutingSource(rtgFilePathName), routingFeatureLayer.FeatureSource);
routingEngine.GeographyUnit = GeographyUnit.Meter; //Set the GeographyUnit.
Any questions please let me know.