Can someone explain to me why the the target # for using the movement critter power on a vehicle is half the vehicles body instead of the object resist? Every other magical effect trying to effect an inanimate object uses the object resist table? Using half the body make the movement power insanely powerful for dealing with vehicles.

A reasonable conclusion would be that the critter is not directly targeting the vehicle, but using its movement powers to lift or otherwise apply force to it (ie, the spirit creates the force, and doesn't directly target the vehicle with magic). The logic then would seem to be that the weight of the vehicle (of which Body is a reasonable representation) is the difficulty of the task.

Consider it a telekinetic manipulation, just as levitate only deals with mass, not OR, movement only deals with mass.

Yeah - an earth elemental would make the ground wrap around the tires, angle upward, or become a 'wave' to carry the vehicle.

An air elemental would lift it, using winds tp push it

A forest spirit would use the surrounding area - trees, vines etc to hold it back (or move it along)