Sorry for bumping this 1 year old thread but I'm having a similar problem with WRC 8 and G29.
1- Mine defaults to 40 and I can't change it. Need to reset it and them it shows 540. I also made a G-Hub profile for the game, with 540 degrees. Game still seems to use something else. I can hardly do any quick turn.
2 - I have to press the accelerator pedal for it to "wake up".
Have you managed to fix it?