Staged disappearance makes sense to an extent. Even LE did not seem to believe that a murder took place (not enough blood, discussed upthread).
But, if this was a staged disappearance, there still should have been one set of footprints in the snow.
Or, could additional footprints/additional tire track shave been snowed over before the car was found? In which case the lack of footprints/tire tracks does not necessarily point to a staged disappearance.
Was the lake already frozen over on that night? Erratic behaviour sometimes points to suicide. Could he have gone into the lake somewhere at an open spot?