First thing: do not use combined axis. It just makes proper acceleration and braking impossible.
And set centering spring to 0% and CHECK the "Enable centering spring in FF games". I'm not sure about this but it should be done this way because of some bug in the drivers(?).
For the FF strenght settings.. there is no right and wrong settings. You just need to try different values and use what feels the best for you. However don't use values over 100% because you will probably just brake your wheel.
What the "wheel turn compensation" does in the LFS controller options?