This is the real problem in a nutshell. If you are in a position to subdue someone like this, make sure the police have to peel him off the floor with a spoon.
As far as NYC gun laws are concerned, don't let them stand in your way. If you are afraid to carry an unlicensed firearm, there is an effective substitute. I would recommend a can of hornet spray and a lighter. If you have a problem with someone in a confined space like this and must resort to any means to protect yourself, the combination of these two can be used to project a long stream of flame at the assailant. This spray is intended to be used on a hornet's nest from a safe distance, so when you use it in this manner you can probably strike someone a full subway car length away from you without having dispersal effects from the flame on adjoining passengers.
Even if you don't actually hit your assailant and he manages to flee the scene, DNA evidence may be obtained from the enormous quantities of piss and crap that he leaves behind.
If the assailant is not armed with a gun but is approaching you from a short distance with a hand weapon, then a brief burst without the lighter will soak him down a bit. That way he will ignite in a particularly impressive manner when you use the flame.
Foaming lye based oven cleaner doesn't have the reach, but it doesn't require a source of ignition, and it doesn't quit burning- little in the face and eyes goes a loooooooong way towards adjusting a naughty person's attitude...
20' stream of nasty stuff with pinpoint accuracy! I'll have to remember that if ever a bad person is between me and my gun.
"If you are afraid to carry an unlicensed firearm, there is an effective substitute. I would recommend a can of hornet spray and a lighter. If you have a problem with someone in a confined space like this and must resort to any means to protect yourself, the combination of these two can be used to project a long stream of flame at the assailant. This spray is intended to be used on a hornet's nest from a safe distance, so when you use it in this manner you can probably strike someone a full subway car length away from you without having dispersal effects from the flame on adjoining passengers."