This is one area where I'm not 100% sure... I BELIEVE if the shooting is a true self defense scenario, that the law stipulates that you can not be charged with carrying a weapon in an off limits location. Again, please double check this...
You misreading the law. There is no law that says that you can't be arrested. There is no law that says that you can't be tried for the crime for which you were arrested. Don't take my word, ask George Zimmerman. The law says self defense is a "defense"--it doesn't say that it is a "bar" to prosecution-- two entirely different legal concepts.
The law doesn't state who or when in the process the determination that it is a defense is to be made. Shooting someone in a "true self defense scenario" isn't a "Get out of jail free" card. The determination of whether it was "true self defense" and therefor a "complete defense" to whatever charge, will always ultimately be made by some trier of fact -- a judge or jury. That's why knowledgeable commentators will always emphasize that that the situation will not be determined by what you know or what you think you know, but by what some third party determines a reasonable person would have done in that situation. We all like to think we are "reasonable person" but you are literally betting your life that some third party will agree with you.