These are the settings I have for my DFGT:
All the axes are 0 because it's not plugged in at the moment.
"Rev." reverses the input when checked, which is needed for the Throttle and Brake because the pedals read 100% when released.
"narrowed" is a setting I have never used with any wheel, I'm not sure what it does.
"Trait" has a series of options for making the axes non-linear, which aren't needed for the DFGT.
You may find you need to go into the Logitech Profiler and adjust settings to make the wheel 900° and split the throttle and brake inputs. I would show a screenshot of how to do this, but the software doesn't work without the wheel plugged in...