Lightning chaser/relentless questions

Hi, got a couple of questions about the genie changes.

Firstly, I have lightning chaser at level 1. I know that it's been changed so that it now has a "chance" to interrupt, but what % does it start at for level 1 skill? Does raising the skill level increase % or is it purely dex that affects it? And do we really need 100 dex to ensure 100% interrupt rate? I'm not even sure that's possible since it takes 2 points per 1 dex when you get it over 40 anyway..

Secondly, am I right in thinking leveling relentless courage only affects duration increase, rather than speed increase?

Thanks in advance for any help on those questions.