Alright, I killed by big scary leader troll-like dude and found Nalia's father's body. Now how do I know when I've completely rid the Keep of the trolls?

I went outside and Nalia said something. There was still a couple of Yuan-Ti on the battlements round the back but it was done. That's the way I remember it (a la Chris Gaines) anyway, but I may remember it wrongly.

You don't have to kill all trolls and yuan-ti. You only have to kill their leader.

After killing Torgal, go outside the keep and Nalia will talk to u. If u r a fighter, monk or barbarian, Nalia will give u the keep as ur stronghold.

you dont have to kill all those nasty trolls, all you have to do is circumcise the leader and the keep's army will handle the rest! (is my spelling correct?)

I presume it is correct.
Haven't you seen my reply above saying generally the same? What is the point of saying it again?

People have a tendency to post and then hit the "back" button on the browser, which doesn't refresh. He probably didn't see your post because it wasn't there.