the sensors skill does effect some part of FOMM, but it might not even be the resistance debuff. might just be the stealth debuff, like that ever made a difference. dont wory to much in specing for FOMM, nearly everyone has a 66% up time on that skill's cure.
heres some research someone did on weapons power, still a remarkable piece of work. as you can see the benefit in the % of extra damage it gives you tapers off at about 150 (on 7 weapon ships), so using more then EPtW1 is really not necessary, and compromises your build really
It only affects the stealth debuff but also increases your resistance to confuse and placate abilitys. Only real use is for the resistance but a fomm on a bop can keep it from cloaking if it tries it while too close.