Anidel,
1. About the icon: There is no proper icon on the left (just the default 4 leaves). There is an icon in the application menu.
2. You are right that with the thumb pressure dependence is more visible.
Maybe mathematically you can stretch the range 0.3-0.5 to 0.1 to 0.9 or something like that? Like y=4 x -1.1 maps one interval to the other.