If CHA did affect charm on live the difference between 100 CHA and max was too small to notice. It did not affect mez and I dont know about lull.
How I'm reading it (i only glanced at it) is charm makes a periodic check (probably per tick) which does use lvl, mr and cha. See here:
http://www.google.com/codesearch#gBb...e\.com&type=cs
Search for "PassCharismaCheck".
Note that this may be modified on P99 and not be accurate here.