Four Wire Resistance -- Three Different Methods 

You could have used an infrared temperature sensor (or even a DMM thermocouple) to document the heating effect.

The voltage leads should be as close to the resistor as possible so as to not include the small voltage drop across the wire. However, it doesn't matter where the current leads are or how long those leads are as the current will always be identical all along a series circuit. If not charge would, of necessity, accumulate at some point in the wire!