Assassin's Kiss gives a passive damage boost when using a dagger; positioning doesn't matter (despite what 'backstab' would imply), it is just random.
With the skill at level 1, if you fight one strong opponent, or multiple opponents with similar defences, you should see double damage about every tenth hit, on average.
Know Creature (level 4) will tell you if an opponent can see you if you mouse over them (or hit Ctrl, for the closest to the mouse cursor), if you don't mind the list of other information. That works with the Embrace Shadows skill, anyway, so I assume does for the survivor's special move, as well.
Try casting level 1 of the survivor's Curse skill on opponents one or more times, and see if that makes Blind more reliable.
For sneaking, IIRC the character should crouch when hiding, and stand up when light, or opening a door, etc, cause the character to unsneak.
