Do what poppe said, you don't delete X and Y, from now on you just edit them, mouseSens should be set to -1, if you don't like to have a 1:1 ratio just set up your X sens and use 0.7 of your X sens for Y.
Note that the ingame sens sliders for X and Y are still inaccurate (decimals are not perfectly matching), if you want a perfect sens matched, you still need to use the configsetting editor.
btw neg accel, polling rate has still not been fixed in STW after 4.4