Please keep heat dissipation in mind.
That it is rated for 165 does not mean that that is without any heat sinking/cooling.
Some napkin math:
Amperage:
400W/12V=33,3A
Voltage drop across Load Switch
33,3A*0,0025Ohm=0,083V
Power Dissipation in Load Switch
0,083V*33,3A = 2,78W
Now your Load...