MRF7S24250N off characteristics are provided in datasheet.
The leakage current is:
IDSS= 10uA max (VGS=0V,VDS=65V)
IGSS= 1uA max (VGS=5V,VDS=0V)
So, R_DS = 6.5 MOhm minimum, R_GS = 5MOhm minimum.
Valid gate-source voltage range is -6V..+10V.
ESD protection clamps below -6V and above 20V.
The gate oxide can tolerate ESD transients but it may fail if the gate voltage exceeds 10V during normal operation.
>... drain-source resistance ... has the MOSFET been broken down?
Make sure that VGS=0 during measurements. If so, the transistor is definitely broken.
