I have test the switch...
pin 1 and 3 in contact when not press
pin 1 and 2 in contact when half press
pin 1, 2 and 3 when full press...
is it OK
From a quick look at the diagram for the later vehicles -
On the 3 pin switch pin 1 is a live feed from F2.
Pin 2 is an output to the ABS ECU (High active - brake on)
Pin 3 is the supply to the brake lights when the switch is pressed.
You should have (if the switch is off the vehicle)
continuity between 2 and 3 at all times. (as they are connected together in the switch according to the diagram)
Continuity from 1 to (2 and 3) when the brake pedal is pressed.
You readings seem totally wrong - although that would not blow the fuse.
It sounds like you have a short circuit in the output feed to the brake lights (wiring short to ground) - or more likely at one of the light fittings themselves.
Note - If you have a trailer socket fitted also check the wiring here as a problem in that area can be common.
As said, the switch should never blow the fuse regardless - the worst case with the switch failing is the brakes are on all the time or off all the time.
I think you need to check your readings again. - with pin 1 and 3 connected at all times the brakes would be on at all times.
As you say the brake fuse blows when you press the switch, it would appear that there is no continuity between 1 and 3 when the switch is NOT pressed ( - you say there is - ) - if there was, the brakes would be on without pressing the pedal.
As the fuse is blown WHEN you press the switch that indicates that the switch IS switching the live feed tot he output. - hence - I would presume the switch is fine and that your readings are incorrect. - the readings you have taken and the description of what happens that you have given are completely opposing.