The previous thing I posted, that file needs to be set to read only if you want to disable mouseaccel in there, I didn't even mention it but mouse accel is in that file too along with the other one ygdrad mentioned.
FOVScale apparently is your ADS/zoomed sensitivity so if you swap it to like 0.33333 or whatever you can actually have two different sensitivities, hope that fixes your problems with it in the OP.