I think his posing ways is because he's a COMPLETE DORK and doesn't know better. I mean. Light (for lack of canon examples) probably has a bigger superiority complex but he's socially sane, and you don't see him pretending he's a thespian. I'd say Lelouch has more of an intellectual arrogance than a superiority complex.
Adrenaline is likely. He didn't seem that shocked to me, though....vomiting is a completely acceptable reaction to gore. The negative reaction of that is more "Oh god I made a corpse" than "Oh god I killed someone", if you ask me. For Euphie....it seemed more like he didn't want to shoot her instead of cannot shooting her. Possible that he knows she wants the same world he wants, considering he knew her personally.
(no subject)
Adrenaline is likely. He didn't seem that shocked to me, though....vomiting is a completely acceptable reaction to gore. The negative reaction of that is more "Oh god I made a corpse" than "Oh god I killed someone", if you ask me. For Euphie....it seemed more like he didn't want to shoot her instead of cannot shooting her. Possible that he knows she wants the same world he wants, considering he knew her personally.