I never did figure out what to do with the grenade -----

The Japanese girl is the hunter that fights the land shark (can't remember what it was called in the game). Her at the temple was a change Wesp5 made some time ago. In the original version with the change, it was buggy and I've not played with a more recent UP but I hear it was nicely fixed in the later versions. I think her name was Yuki.

I know about this, it might be another AI problem. He is set to be afraid of you but he will still fight you! Update: I have found a way so he will not attack you but just cover or run away :). Expect this in the UP 9.6! I made her not follow you down because it's difficult enough for her to not get stuck in the first map ;). Both of this seems to be intended. Nadia will never follow you into the lower area...

As for the grenade, sometimes it's buggy. But it isn't of much good use anyway :(!

It would be the best if he leaves when persuasion line is used cos persuasion is not about being afraid but rather about reasonable approach. Other thing is if this can be done without recompiling the map.

She follows you until the point where she says she is not coming any further and is heading back. But you have to kill all zombies first for her to come I think.

And about Yuki there should be a dialog triggered where she says you have to go alone from now. It's should happen in the final area (with stairs going down) of first map. Then she should leave the building and stay near a wall opposite to the building. At least from what I remember. Also in 9.4 she starts to follow you again (but only on the first map) if you go near her. Not sure if the last thing has been fixed for 9.5.

I don't think this is possible at all, except him simply vanishing in front of the main doors which looks weird. I think fleeing is still a vaild reaction to Persuasion as it's clear that the player will kill him otherwise...

He can flee through the door :) And it doesn't matter it looks wierd since it's much more logical. What he does right now is much more adequate for intimidation but I think that even in case of intimidation he shouldn't shoot to you cos if a player choose this option then it means he/she rather don't want to kill him.

I hate teleporting NPCs, it kills immersion for me big time! Right now in 9.6 he will run away and try to hide, like even behind his desk :)...

I have seen in many games that chars run to a door and disappear. For me it would not be a problem.

If there is another room behind the door, its best when the char opens the door, goes through it, the door closesand then he disappears. But if this is not possible, its better that the char disappears at the door that to have a char in the room that is supposed to leave.

As somebody has said before:
If you intimidate him, his behaviour makes sense. (though even then, leaving the building makes more sense)
If you persuate him, he should leave the building.