He's looking to defend himself and help his buddies, not decimate people and lose all his personal wealth or spend time in jail for assault. The more you hurt someone above what you needed to stop them, the more likely you're gonna wind up losing everything, or spending some time in jail.
I make my suggestions based on "no other way out" type situations. Believe me, I am the first person to walk away from a confrontation if at all possible, for the very reasons stated. 9.9 times out of 10, if you make all reasonable attempts to get out of a situation, but the other guy just won't let you (admit it guys, you've all known of situations like this), even if you slit him open with an elbow the cops will say it was self defense. It all boils down to being smart, and knowing your surroundings.