Origin of "BREAK A LEG"

Over the years I have been involved with many theater productions, and actors seem to have some strange "superstitions". But one of the strangest is to never say "Good Luck" to someone before a performance.
Wishing one "good luck" is bad luck. But saying "Break a leg" is good luck.
Why are actors so backward? I researched the meaning behind such a dumb tradition and this is what I discovered.

Actors have always been a superstitious bunch, as you might expect from a profession in which employment is sporadic, audiences fickle and reputations fragile.

The saying is widely used among actors and musicians in the theatre today, sometimes before every performance, but more often reserved for first night. Where it comes from has for decades been a source of dispute and here are some speculations:

* In earlier times, actors wished one another “may you break your leg”, in the hope that the performance would be so successful that the performer would be called forth to take a bow — to bend his knee.
* At one time audiences showed their appreciation by throwing money on the stage; to pick the coins up, actors had to break their legs, that is, kneel or bend down.
* The curtains on either side of a stage were called the legs, so that to pass through the legs was to make it out on to the stage ready to give a good performance, or perhaps expressing the hope that you will need to pass through them at the end of the show to take a curtain call, implying your performance had been good.
* The saying really refers to getting one’s big break, that the performance will be good enough to ensure success in one’s career.
* The famous French actress Sarah Bernhardt had a leg amputated in 1915, which didn’t stop her performing; it is considered good luck to mention her in the hope that some of her theatrical prowess will rub off by association.
* John Wilkes Booth, the actor who assassinated President Lincoln, broke his leg when he jumped on to the stage to escape afterward. Somehow, reminding fellow actors of this event is supposed to lead to good luck in the performance.

The above leaves me to wonder:

If John Wilkes Booth had strained his groin, how may the saying have changed?

I also wonder if football players say "Break a nose"' or "Sip your soup" for luck...or as big as they are, maybe they can say "Good Luck" without worry.