I recommend you take a defensive handgun class offered by a reputable training company somewhere on the mainland at your earliest opportunity.
The Front Sight 5-day Defensive Handgun Class not only qualified me and helped with the paperwork for several non-resident CCW permits. They also gave classroom and hands-on instruction in a variety of topics dealing with defensive uses of guns (DUG). That included various laws of states, permit reciprocity, deescalation of situations, etc.
When you carry in public, you are a totally different person. You know you have a firearm within a second or two of being able to use it. You also know that you have the power to end someone's life -- justified or not.
When you think saying, "don't get any closer if you intend to harm me", is reasonable, proper training will tell you that's not how it's done. You need to make your commands and declarations simple, concise and easy to follow. Saying, "if you intend to harm me," not only invites the threat to continue approaching because he SAID he's not threatening you leaves the door open for him to still attack when he's close enough. It also indicates you're not in charge -- he is, by virtue of you telling him his intentions are driving the situation.
You yell, "Don't come any closer! Stop right there!" If they continue, then say, "I told you to stop. I will shoot you if you come closer! Leave now!" If the threat becomes more immediate, you will have to assess if you feel your life is in danger. If you draw your weapon, you are legally obligated to fire unless the threat retreats upon sight of your weapon. If you brandish a gun with no intention to use it, you can be charged with brandishing, assault, and assault with a deadly weapon. If you didn't think you were in sufficient danger to fire, why did you draw your weapon? It's a legal snafu that DAs will get you on. "I was just trying to scare him away," is no justification in most states.
Rule of thumb: never draw your weapon until you are prepared to use it. Same rule applies to firing a warning shot. If you felt threatened enough to do that, you should have felt threatened enough to aim that warning shot at the attacker's chest. Guns are not warning devices for civilians. They are a last-resort defensive weapon -- that's WEAPON! Would you point a knife at someone to convince them you are serious? What about a bow and arrow? Weapons are for defending yourself, not for causing fear.
Legislature does not need to codify warnings. We already see where any "magic words" required by law can be simply stated by the Cop or defending individual, such as "I was in fear for my life." Those words are difficult to refute, and they rise to the level necessary to justify pulling a trigger. If saying, "I have a gun. Stop or I'll shoot you!" are codified, guess what words the intended victim will be instructed by lawyers to say they said? Without a witness or video with sound, it'll be your word as to what was said. Not very effective, huh?
The reverse can also be problematic. If granny doesn't say the magic words required by law, and she stops a guy following her in a parking lot just seconds from him being on top of her, does she forfeit the justification of self defense?
These situations happen in seconds usually, and no specified group of words will deescalate them all.
When you're carrying, and someone talks smack to you, it's easier to just walk away. It's preferable to ending another life and then dealing with the legal and emotional aftermath.
If you're truly the victim, you may have no choice in escalation or deescalation. The other person/s has the choice to stop, continue or ratchet it up if you don't respond. Depending on the other person's intentions, a physical altercation may be a predetermined outcome. No law or specific words will prevent escalation, and the escalation will be all one-sided.
As a correction to your comment, Tasers are considered less-lethal weapons, not non-lethal. People have died from being Tasered. Most, if not all, of the rules of engagement that apply to firearms should apply to Tasers. So says the President of TASER International:
Less-lethal is a means of acknowledging that all uses of force carry some finite
level of risk -- and it removes the semantic debate over "non-lethal" from the court defense of any
less-lethal weapon. Less-lethal is the generally preferred terminology used today for everything from
OC to batons. So, we too have adopted the terminology "less-lethal" to describe all of our weapon
systems, from 7 Watts up to 26 Watts.
https://www.prisonlegalnews.org/media/publications/taser_intl_less-lethal_v_non-lethal.pdfThink about it. If someone is a perceived threat, do you really want to play your trump card (draw your weapon) before you absolutely have to? Do you want to advertise you're armed, giving them time to formulate a way to relieve you of it, or come up with a way to counter your weapon? Letting people know you're armed is not always the best move. Even if nothing happens, if you advertise you are armed, what's to stop the bully from calling 911 and lying to the Cops that you were waving your gun around and threatening them? Better to just not say anything and walk away. You're the one armed with a firearm. Who do you think most Cops are going to be focused on?
Best advise is to call 911 and leave the line open. As the situation escalates, everything will be recorded that's picked up on the phone call. If you handle yourself properly, everything you say and do will be evidence that you did all that you could to avoid having to pull the trigger.
If you didn't have time to call 911, you probably didn't have much time to have a conversation before being attacked either.