Lexington Park means Solomons or the St Mary's City area. I'm not sure about liveaboard space there, although I believe there are places.
For Columbia it will be a commute at the extreme end of your criteria from Annapolis, the Magothy River, or Baltimore. In Baltimore talk to Baltimore Marine Center or the Anchorage. In the Magothy talk to Magothy Marina. In Annapolis, try Eastport Yacht Center, Port Annapolis, Annapolis Landing Marina, and Jabins Yacht Yard.