Hi, a patch from a month after you posted this increased the sensitivity range. In game I can reduce it to 0.03 and raise to 0.99, with increments of 0.02.
However, it's possible to go outside the boundary. I did a bit of digging with the sensitivity value. It's a binary file stored in "%LOCALAPPDATA%\P3\Saved\SaveGames\GameSettings.sav".
I made a quick script to update the settings to any value (https://gist.github.com/huntfx/613461d817d957d644c2092b6d37d91a).
Updating the 4 values allows for as much precision as a floating point number can handle (eg. works with 0.00001, even though the UI says 0) and doesn't revert back to the 0.03 limit, so actually works very nicely.
I managed to figure out my sensitivity at around 0.0165 which was a little difficult with the limits built into the website - if anything it would be great if there was a "force 0% discrepancy" option to bypass any limits.