A few years have passed since this got chopped off, interesting. A lot of people assumed a number of things and, with the original poster not present, assumptions continue in lieu of questions.
"You've gone out to dinner with your SO ... when you walked out to your car in the parking lot there are only a few cars left ... As you near your car, you see 3 guys sitting on the trunk of another car blocking your path to your car."
With few cars in the lot and BGs' close to GGs, it means that you will see them from a distance. This is the time to take a long, hard look at them and then go back into the place and drag the boss out and point at them and ask him to nod and go back in - the BGs should assume that they have been made. If that isn't possible, take out your cell phone and punch a short number - most PDs in most places will have a RPC roll by, just to show the shield and provide preventive support if they aren't busy elsewhere.
Assuming that doesn't work or you are negligent in situational awareness and the furthe scene ensues -
"You try to get around them and two of them jump off their car and one guy immediately whips out a snubbie and points it at your head. The other guy makes rude noises about what he'd like to do with your SO."
Your hand should have already been on your weapon, ready to draw, with your SO in a position behind you and watching your 6 - all this depends on which one of you is best at what follows, of course. SO might want some target practice. By the time
"BG-1 tells BG-2 to "off the guy" so they can have fun with your SO."
the armed BG should be full of your favorite holes and not moving any more. With their vehicle as a nice backdrop, rate of fire can be increased. There whould also have been enough distance for you to have chosen your field of fire - no one approaches such a situation as the BGs have planned it - your analogue OODA system has generated plans to execute so do it at a good distance, which should favor you. They have one snubbie, you have... whaaaat? You didn't take the big boy out for a walk tonight and just have your pocket mouse gun with you? You the guy who doesn't believe in carrying serious steel?
The other BGs are co-assailants in an armed assault. In Florida, if one of them goes dead, they get charged with murder (1, I believe). I suppose there are other states in which GG would be put away for using excessive force.
You are still trying to figure out what happened, hoo boy...
"You figured it was a simple robbery up to this point, but the minute you hear "off the guy." You see that BG-2 has his eyes off of you..... You draw your CCW and you both fire at the same time. BG-2 goes down and you feel a sharp pain in your gun hand. Bg-1 is moving towards BG-2 and his gun......
....do you switch to weak hand and try to nail BG-2? or do you try to toss your CCW to your SO? or do you choose to do something else? What? Oh by the way, BG-3 is moving quickly towards you? Now what?"
Do a quick function test by shooting at the closest BG or once at BG 2 if he is really close to getting the gun. If the weapon is damaged, you cannot shoot, or cannot shoot well, you should have moved your weak-side hand (which is now your strong side hand) to take out your BUG and start shooting one shot at the most serious threat, two at the closest threat and back to the other BG. Save some for BG 1, who may be down but not out.
Whaaaaaat ?!? You the guy who doesn't believe in a backup gun? Well, then you need to be getting that weapon into shooting. You might also try running back to the restaurant, as the shooting must have caused a stir.
Trouble with scenarios like these is that they tend to be so open and iffy that it is difficult to come up with a clear answer.
Oh yeah, don't toss the piect to SO, get it working in either of your hands, if you can. Backpedaling while this is going on isn't a bad idea, either - keeps distance betweek you and BGs.
