You may need to go into windows game controller properties, through the windows control panel and you should/might be able to seperate the axis under advanced properties. (if you use the wingman profiler you can also access it from that)
Also in LFS you should see the option to combine/seperate axis in the list above where you set the axis up.
You need to have both set to seperate in order to get the gas and brake indipendant from each other.
Some wheels do not allow seperate axis, I'm not 100% sure about yours tho
Good luck.
SD.