in FL, you cannot legally shoot someone unless you fear for your life. it's up to a jury to decide if you really feared for your life. A little old lady could shoot at a 300 pound BBer who is about to lunge, and a jury would let her off the hook. But a 300 pound Bber couldn't shoot the same little old lady who was ready to lunge.
A very gray area there - Juries decide. So unless you're in a spot where you CANNOT flee, your ass needs to at least make an effort to flee. Yes, the law says you don't have to, but really you don't want to shoot someone unless absolutely unavoidable. If you have a chance to just back down to avoid shooting someone - YOU TAKE THAT CHANCE. most fights, right or wrong, you can say sorry, i give up, tap out, etc, and they'll stop. If not, and you can't flee, you do what you have to do.
But all this "Can I shoot someone if..." with a dozen fansasy scenarious they have... that sucks.