Rogue traits

[MikeXG]

On the wiki there are a few cool 50+ rogue traits listed:

Level 50+ Rogue Traits

Level 53 - Minimum Backstab Damage
Level 55 - Double Backstab Chance, Sneak Speed starts to increase
Level 57 - Bind Wound Cap Increased to 70% health once 201+ skill attained.
Level 60 - Chance to Assassinate level 46 and below Humanoids when using Backstab or Thrown, Sneak Speed maxed out


Does anyone know how the minimum backstab damage is calculated?
What % chance is there to double back stab?

Thanks!