Regarding the 4WD, start by determining if the pump has power & ground - there are three wires in the harness to the pump - pink, red & black - should be 12v between red & black but it'll only be there for 10 seconds or so, if the controller doesn't see the system engaging. If you do have 12v, short the red & pink together and see if the 4WD light turns on, could be a bad bulb.
Re-the rattle - fit an oil pressure gauge and see what the pressure is like when the engine is hot.