There are several places that fit your request.
First, I agree that Brewer's Art is a good choice. Inventive food and good value as they are including a house made beer with their RW menu (eating at the bar is always welcome). Second, Jack's Bistro in Canton. Also very inventive and solo friendly at the bar. However, no real price or menu advantage during RW. Third, The Wine Market. One of the few to offer a 20.10 lunch during RW and only 30.10 for dinner. Small but welcoming bar at which to eat and 10% off any bottles of wine you may want to take home after dinner. Finally, Salt Tavern. I have eaten at the bar alone many times at Salt and can tell you I prefer it. No real RW deal, but among Baltimore's best restaurants.
I believe that any or all of these will give you a good idea of "Modern American" in Baltimore. None of therse are classic Baltimore restaurants in the sense that they have only been around for less than 15 years, but they tell the story of emerging Baltimore.
Also, while not in RW the bar at Charleston is now happily welcoming individuals to eat one or two courses. It's a great opportunity to sample the food of what many consider the best restaurant in Baltimore without having to have a full menu.
As an aside, if you make it to Howard County , Victoria's Gastro Pub in Columbia has the best Howard County RW lunch menu at 12.50.
re: Trip Klaus
In addition, most any of the places in Federal Hill or Canton on the main drag will probably have a pretty busy bar where you wouldn't feel uncomfortable sitting and ordering a meal. You'll probably run into the same issue though that the menu isn't expensive enough to be a great RW deal. Are you looking for lunch or dinner?