Hardware, Software, & a Real Mess
It seems most subways/trains are in places that have laws against carrying weapons for self defense or even self-defense itself. So, bringing my buddies Smith and Wesson to the party is likely a non-starter.
SOFTWARE
My first response to the mess would be to stand up and put on my old Ranger Face.
If that did not do the trick, I would have used some old-school verbal commands in a manner to make my old drill sergeants proud.
[If I was required to use verbal commands, I would have gotten off at the next stop. No sense letting them stew over a verbal beat-down and rally their courage.]
If neither RF or verbal commands work and they persist in escalation before I can get off the train, I move toward the exit doors and keep my back to the doors, if possible, and get off the train at the next stop.
[If I am crowded or advanced on in my retreat, I give that person--at minimum--a strike to the throat. Why? Such an advance on their part constitutes that they are following and attempting to prevent me from leaving. I will have performed the (likely legally obligatory in non-free states) attempt to retreat and it was not successful. Time to go to Fist City. Also, the aggressors in the video and in such situations do not get into any sort of fighting stance it seems, and do not lower their jaw & head to cover their throat...and it takes less force to incapacitate with a throat strike than most others.]
If it starts to go to a physical confrontation, I would retaliate with violence as extreme as I could muster. What would that require? A chest bump, push, or that knucklehead trying to whomp me with the bottle. I am not a cop trying to subdue anyone and I am not anyone's punching bag. I would not attempt to restrain, hold, or the like, with multiple attackers. I would aim for the most debilitating blow, every time, until I was out of harm's way or incapacitated.
If I were still standing when the next stop arrived, I would do my best to exit & run off and call 911 when I am in a relatively safe place. I have no doubt that if the situation got physical and I got away, that some of my attackers would require medical treatment and the story would get to the police. Best to get my side in the hopper and report it ASAP.
HARDWARE
Frankly, in this sort of situation, software is much more important than hardware, hardware being heavily restricted.
If legal, I would have a concealed firearm. Truthfully, I am not sure the close confines of the train car and the numerous bystanders make it the best weapon for the job.
If I legally were able to, I would carry a knife. My usual carry knife is a slick, light, ~3" blade Beretta quick-open job. The knife would be used if the pack got violent. It would have been easy enough to have it palmed in my hand at the first sign of trouble. If the pack got violent, it would be open, looking for throats & other such targets. My purpose would NOT be to inflict superficial cuts here & there. Multiple attackers are a real threat to life & limb. I would respond likewise. Perhaps seeing one of their number on the floor bleeding like a stuck pig would give pause to the pack.
If a knife is not an option, I can bring my Surefire 6P about anywhere. It would also be in my fist at the first sign of trouble and would lend heft to any blows. A roll of pennies performs the same function.
I am not a big fan of OC, as I have eaten some of it and still been able to function at close quarters. I assume I am not unique. Also, do I really want to let OC loose in a confined train car? Not only would my attackers get a snootfull, but everyone else in the car would get some, too.
WIFE & KIDS
OK, why don't we make this scenario really stinking hairy. I/you are not alone facing the pack. Your wife & kids (let us assume toddlers) are with you.
I would still respond, initially, with my Ranger Face and then verbal commands. Even if I just used the RF, I would get the family off at the next stop. I will not fiddle around, I will get my family outta Dodge ASAP if I think the situation is hinky.
If neither RF nor verbal commands work, it is getting ugly, because you just plain can not retreat in the face of a threat with your family right there. Edging over to the exit door to slip out quick-like at the next stop is not possible with little kids or, really, with any group larger than two.
If the exit arrives before it has gotten physical, I use verbal commands to ge tthe pack members out of the way and make serious theats to hurt any who prevent our exit.
If it gets physical before the exit arrives I do not spare any means to incapacitate the attackers in the quickest way possible with whatever I have at hand: firearm, knife, OC, whatever. I instruct my wife to keep the kids clear and move out, away from the struggle, into another car, if need be and to get off when the next stop arrives. If the exit arrives during the struggle, I keep up the struggle while my wife gets the kids outta there.
Man, that would be a mess and a nightmare. I don't think I want to take my family to NYC...or use public transportation of any sort, now that I think on it.