I have been a police officer(Sgt) in Va. For 35 years. In order to use deadly force justifiably 3 criteria must be met.
1-you must be in fear of death or grave bodily harm(or someone around you).
2-the attack must be immediate and unavoidable.
3-the attacker must have the means to carry out the threat.
As for carrying concealed. You get an application from the clerk of the court of you jurisdiction. You must have completed a handgun safety course or have prior training like the military or hunting safety course. Once the app is returned the state has 45 days to approve it or the actual application becomes your permit until the approval comes, so make a photocopy.
You can carry in any establishment that serves alcohol as long as you don't drink. You can carry in a house of worship "with good cause". You cannot carry on federal property unless it's on the approved list. No airport property, no courts, no post office. Remember, some airports like Dulles have private access roads. They are considered federal property.
If you carry concealed properly and discretely no one will no you are carrying. The gun is your weapon of last resort. It is the final option.