Hi,
I'm using a G27 wheel.
I play with 360° rotation, 300 is way too sensitive.
The deadzone can be configured in the dosbox configuration file, by default it's set to 10, it's unplayable. Set it to 0 unless you have some weird behaviors in a straight line (oscillation around the center)
I you have some jittering/oscillation in the values, try setting the "timed" option to true in the configuration file, it helped me.