+% Critical Chance from Rage

[Marlowe]

I'm not sure if it answers all your questions, but if you you use the interface mod (available in the Mods forum) you can see the percentage chance to crit for each unit (enemy units too). It also shows the percentage of increased damage for a critical hit (this also increases with the amount of rage, which I don't recall seeing in any of the documentation). The mod also has many other nice additions to the UI and I find it very worthwhile..