No such thing as optimal settings, it's all about you feeling comfortable driving the car.
In my experience, raising linearity makes the car less nervous on straights and helps you transition smoothly between straight and cornering, very important in this game in which smoothness is everything (agressive corner entry is not at all rewarded), i'm up to 50% now (disregard my earlier post) and it feels a lot better.
I know from other sims to stay away from deadzone, i don't like it at all and this apply's here, saturation seemed like some kind of "reverse deadzone" in early Codemasters titles so i don't mess with it.
Regarding FFB 10% wheel wheight because i like a light steering that doesn't make me use my strength.
Most importantly, set OVERRIDE INPUT DEVICE to STEERING WHEEL, otherwise the game assumes you are on a gamepad and forces some kind of steering help on you (which is not helpfull at all for wheels).
But again this is all very personal, use it as a guideline