You also need the thermal resistance for your MOSFET, expressed in °C/W, for junction to case (Θjc) and for Θca (case to ambient) and the Θ for the heat sink you'll probably be needing.
So then you have a series thermal circuit with "thermal resistances" and °C being analogous to voltage. You want to keep the junction temp below some value, probably <150°C.
Ohms law without the ohms.
Spreading the heat generated in the tiny volume of the MOSFET junction over a large surface area exposed to ambient temp is the goal.
Service lifetime for circuits and a lot of other things halves for each 10°C rise above ambient.
Can't open your attachment; my problem. Can you excerpt parts of the sheet?