You've been reading too many romance novels. Those dime store books have not told an honest story of the west, but rather a fictional story of the west.
Simply put, although there were duels fought in the streets, no one in there right mind would stand to an opponent if he could shoot him in the back. Better still, shoot him where there were no witnesses. There is nothing in this game that even remotely represents justice or the truth of the west. We are unable to refuse a duel. If challenged, we have no choice but to fight, and in the dumbest way possible, facing our opponent.
Now, I understand that you want to just go around killing people, but how about this for the Sheriff, the Mayor appoints him, the Sheriff can appoint deputies (Number dependent on the population). If an outsider calls the worker (not adventurer) out to a duel, there is a chance that law enforcement will step in and break up the fight, putting the offender in jail (most of the time), and sometimes the worker. If the challenge was to an adventurer, after the duel, the sheriff might for a possie and chase done the person who attacked his adventurer.
One must never forget that justice did actually exist in the West of the 1880's. It was even romanticized by radio and television dramas in the 1950's and 1960's.