Boxing is a sport it can be useful in a self defense arena but it is limited by rules, range and training in these rules.

How in the street is it limited by rules? A boxer can only do certain things in the ring, that doesn't mean he can't resort to other tactics besides his boxing ina street fight. I am always amazed by people who say that people trained in "sport MA's" are somehow ata disadvantage because they have rules to their matches. Yes, there are rules in the ring, but when you are a boxer and not in the ring, you are free to improvise and add to the skills you already have, including using "foul tactics" just as much as a karate practitioner or anybody else.