The OP says he lives in Florida. There are no CCW classes required in Florida.
As to the law, what the OP talks about does seem to fall into legit self defense in most places.
Florida, as well as many others, allow for deadly force to prevent or stop the commission of a "forcible felony" or similar language. Florida statute 776.08 defines this as:
776.08 Forcible felony.--"Forcible felony" means treason; murder; manslaughter; sexual battery; carjacking; home-invasion robbery; robbery; burglary; arson; kidnapping; aggravated assault; aggravated battery; aggravated stalking; aircraft piracy; unlawful throwing, placing, or discharging of a destructive device or bomb; and any other felony which involves the use or threat of physical force or violence against any individual.
Florida statutes in part 776.013 covers the use of deadly force to protect the home.
776.013 Home protection; use of deadly force; presumption of fear of death or great bodily harm.--
(1) A person is presumed to have held a reasonable fear of imminent peril of death or great bodily harm to himself or herself or another when using defensive force that is intended or likely to cause death or great bodily harm to another if:
(a) The person against whom the defensive force was used was in the process of unlawfully and forcefully entering, or had unlawfully and forcibly entered, a dwelling, residence, or occupied vehicle, or if that person had removed or was attempting to remove another against that person's will from the dwelling, residence, or occupied vehicle; and
b) The person who uses defensive force knew or had reason to believe that an unlawful and forcible entry or unlawful and forcible act was occurring or had occurred.
(3) A person who is not engaged in an unlawful activity and who is attacked in any other place where he or she has a right to be has no duty to retreat and has the right to stand his or her ground and meet force with force, including deadly force if he or she reasonably believes it is necessary to do so to prevent death or great bodily harm to himself or herself or another or to prevent the commission of a forcible felony.
(4) A person who unlawfully and by force enters or attempts to enter a person's dwelling, residence, or occupied vehicle is presumed to be doing so with the intent to commit an unlawful act involving force or violence.
So, it appears that someone in the process of breaking into your home is subject to the use of deadly force.
There are some exceptions in the law so it's worth reading in it's entirety for sure. I didn't post all those, that's why section (2) is missing from above. It's rather long. Link below to the whole thing.
So you're presumed to be in fear of your life if someone is kicking down the door, regardless of whether or not they are armed.
That's pretty standard for states with so called "Castle Doctrines". All that said, you still have to convince a prosecutor that you were in the right on all the legal points.
So, in general, yes you could use deadly force against someone who is outside your home purely from a theoretical legal point of view if they are committing one of the listed crimes.
http://www.leg.state.fl.us/statuTes/index.cfm?App_mode=Display_Statute&URL=Ch0776/titl0776.htm
Not legal advice, all the usual disclaimers, just citing the statutes. Everyone has to decide this stuff for themselves. There are moral questions here that the law can't begin to cover.