Speaking as a fellow north Jersey chicken lover....get rid of that heat lamp or you will risk burning down the coop, your house, and your neighbor's house! Remember, wood shavings and chicken feathers are very flammable, not to mention that temperature can rise quickly to roast the chickens in such small coop.
After surviving my first cold winter with 4 young chickens last year, when there were times that temperature dipped down to -10F at nights, the chickens were fine. I lived to have some good night sleep too after staring at the thermometer and humidity gauge for a couple late nights. Granted, we have an insulated coop, but the coop windows and pop door are always opened for ventilation, even in the dead of the winter, so the temperature inside and outside the coop are the same. Don't worry, the chickens can make themselves into a puff ball to retain body heat. Being that your coop is situated between buildings, it is well sheltered from the wind. New Jersey is really not that cold compare to some other places where people have successfully raised chickens without the danger of using a heat lamp.
I would suggest that you raise the roosting bar by a couple inches so the chickens don't get back-splashed by their own poop dropping at night. Make the roosting bar 4" wide so the chickens can flatten and sit on their toes to keep their feet warm. Increase ventilation (to provide still fresh air) as much as you can to minimize smell and condensation build up.
Like the others have mentioned, 2 chickens are fine with that coop. Resist chicken math, or a much bigger coop will be needed.
We too got our chicks from Moyer last June.