One amazing place to have dinner is Top of the Hub in boston, one of my favorite places for sure. Amazing view and amazing food. Not really the "hole in the wall" place your looking for though. But just in case your ever up for a nice dinner thats the place to go.
I have been in salem for halloween before and just a heads up. Be prepared to be stuck in traffic and large crowds ALL night haha. Sorry I cant give advice on the bars, I dont ever go.