JR is on L Street, between Connecticut and 18th Street. It is 1/2 block from the Farragut North Metro stop Red Line, (the L St exit). Not sure if there is a place to sit.
W. Curtis Draper on 640 14th Street, I think between F and G. A shop that has been in DC for at least 40 years. Excellent selection plus pipes, pipe tobacco. Prices seem fair, as I recall. About 1-1/2 blocks from the Metro Center subway stop (13th & G exit).
Around the corner, at 1331 F, near 14th is Shelley's Backroom. It is one of the only restaurants/bars in DC in which you can smoke. You can bring your own cigar or buy one (expensive) there.
If you get over to Georgetown, on M, a few stores east of Wisconsin Avenue, is Georgetown Tobacco, an old-time tobacco store. Excellent selection and fair prices. A few places to sit. No subway to Georgetown, though.
All of these are walkable, though Georgetown is a long walk and you would be happier taking a cab. W. Curtis Draper is probably the closest and may take you 20 minutes to walk.