Does Zakum drop ACB 10 often?

So I have recently turned into a Paladin. I would like to know from those who zakum regularly does acb drop often?
Do Zakum runners let people who need ACB to go in for free and get the ACB book for free?

Often? I would estimate 1 in 4 runs or so?

As for letting strangers join a run, I suppose that really depends on the runner(s) and their reason for zrunning.
Don't you have any friends, or friends' friends, who can kill zak for you? As a paladin you can help quite a bit with CO and Threaten, even if you don't do much damage yet.