1. The Query1 not unique error is probably coming from the ExplorerListViewModelLinked class. In your code, you are passing your query and a keyfields object to the ExplorerListViewModelLinked class. The keyfields object must contain fields that when combined form a key on your table. You are not passing a key. Try passing in btschinf_num_new.
2. Try ExplorerListView_RecordChanged which should accept two arguments, the member changing and the current record selected in the ExplorerListView.
3. ExplorerListView does not automatically refresh its data, so users would have to exit and go back to see changes made by other users.