If Long Island and Queens are unscathed, who cares about a little damage to Manhattan? It hardly matters. Even most of Manhattan would continue with business like normal from a couple hundred tiny warheads. They'd clean up the rubble in a day, and then call in construction crews to repair the damage, and move on with business.
The point you are missing here is that Iran can lob missiles on Israel anytime it wants. They still have a large stockpile, and will replenish older missiles used with new ones that are even harder to stop. If NYC were under missile fire or just the possibility of that, real estate price in Manhattan would collapse, businesses and HQ would move out, as would many residents. And I wouldn't call 1 ton warheads "tiny", or downplay the kinetic force of large metallic objects making an impact at mach 5 or above.