Andrew, regarding the aircraft weathervaning into wind and drifting with the wind, these are two very different things.
On the ground the aircraft cannot drift, just weathercock into wind, while in the air the aircraft drifts with the wind.
The reason for weathercocking into wind is quite simple - the wind blows on the side of the aircraft, but the tail presents a much greater surface than the nose, so there is a far greater moment acting behind the main wheels (the pivot point), which means that there is a tendency to turn into wind - unless counteracted by nose-wheel steering or rudder input (whichever has authority for the phase of take-off or landing).
Hope this is clear
FBW