Donald Trump wants to arm teachers with guns

[A Theist]

How many illegal guns that the police and local authorities don't know about would you estimate are in the hands of criminals in our cities?  How would the anti second amendment proponents go about getting those off the streets?

In proportion, about as many as you'd find in any other place on Earth. Perhaps even less, because if you can get guns legally, there's no drive to get them illegally.
Please don't muddle the discussion with things that are beyond our control and represent the same background level in gun related death across the whole world.

There's no muddling about it. If you're going to address gun violence you can't ignore the shooting deaths by criminals and gang members with illegal guns in cities like Chicago, for example, that have strict gun laws.