Temperature drops 1.98°C every 1000ft up to FL360 where it remains constant at -56,5°C.
FL380 at ISA + 5° means -56,5+5=-51,5°C
Headwind means that groundspeed will be lower than TAS, so TAS will be 453+58=511kts.
You have what you need. Remember to convert °C in K before using the temperature in the LSS formula.