I can kill the panthers, also the bodyguard, but whenever I try to take the knife and throw it to the boss I get crash. Is there some kind of cheat to get past this because I am quite tired of this BS?

That's all right, don't sweat on it. :)
I like this game quite bit, but for me it has been bit unstable at times.

I managed to kill the boss, but was standing just to the right of him when it happened. After his scripted bit I got a Chapter Cleared! and died at the exact same moment. After that, music wasn't playing while I kept trying to kill the boss, when I finally managed it, it dropped to desktop. Now every time I try to start the game, I just get a bunch of exceptions