Until you can diagnose the problem properly you could pull the #4 or 5 fuse (depending on model year) instead of disconnecting the battery. That should stop the pump. While you are there look for a sing of possibly jumped #4 and # 6 fuse (or 5 to 7 on earlier model). That would bypass the fuel pump circuitry all together, resulting in the symptoms you describe. Since the power to fuel pump relay is cut by the main relay whenever ignition is off, sticky fuel pump on it's own could not be only source of the problem.