What temperature should I use for desoldering a component?

MOSFETS got a high surface that allows to dissipate the temperature. That process will be tricky also because of usage of non-PB solder. 380C set would be ~330-340 effective heat on the component, which is barely enough to solder, and way to low for desoldering such heat dissipating element. Be careful thou, because glass-resin PCBs likes to boil at higher temps, which is deadly for multi-layer ones like in laptops. Consider pre-heating whole PCB with a heatbed or just the area around the component with air gun.

What I would do:

1. Lots of lots of flux.
2. Add solder tin with PB using your iron to lower the melting temperature - especially at the gate/ground/NC-radiator-pin (whatever it is the largest surface)
3. Take away most of the tin
4. Reapply flux. Lots.
5. Heat it up with air ~400-420 should be fine if you would be fast.

Good luck!