Some more tries, as I would really regret to have to kill Scratch.
So, restoring the save once more, I did kill scratch with a critical hit in the first round. Then combat was over and none of the other NPC's attacked.
I tried again, this time Gale had the first initiative. He cast sleep on the dog, and even without any physical attack, the dog falling asleep triggered Astarion, shouting something like "now you get it" -- or something like that, I forgot the exact phrase -- and attacking Gale. Wyll at this time was not yet part of the battle.
I stopped it, I 'm not in the mood to fight my own party. I hope there's a way out.
