There is also construction on I-95 through south Baltimore, prior to the Ft. McHenry Tunnel. There is a lane split and a lot of signage, barrels, jersey walls, etc. Just stay left when the lanes split and keep your eyes open so you don't accidentally get into an exit lane.
No matter what, plan your schedule so that you get into Baltimore AFTER 6pm, so you will miss the rush hour (assuming you are driving on a weekday).
DCs rush hour runs much later, but if you hit Baltimore after 6, you won't hit DC till aftter 7, so the rush will be done there as well.