My Glock 17 always has 17 rounds in it, and I have two 33 round back up magazines. If I was going into a situation that felt really scary, that would be my handgun of choice, and it would conceal well enough if it had to.
But in the situation presented, I don't know that I would bring back up magazines, although I would have my R9 as a bug. So, I'd have 24 rounds, anyway, which would hopefully make a difference.
The big problem is that in NJ, in the scenario presented, I wouldn't be able to carry any guns -- New Jersey doesn't give carry permits except in rare circumstances. So... it would really be a fight to the door with my pocket knife.
Just as a side note, though, I have two uncles who live in -- you guessed it -- West Milford, NJ, right on Upper Greenwood Lake. And one of them is a state trooper. Next time I see them I'll ask if there is any truth to this story.
You could post a million hypothetical situations here, but the answers to all of them would be pretty similar. Be always armed, aware of your surroundings and anything suspicious, and trust your gut feelings. Get out early if something doesn't feel right. And surround yourself with people you can trust who are also armed and aware.