Live in Baltimore specifically Mt. Vernon, or Hampden if you're alright with a quick bike ride down the fallsway to Penn station and commute to Union. It's significantly cheaper from a cost of living perspective and a decent area in the city.

Edit: I also commute to DC twice a week and live in NE Baltimore, based on your other comments anywhere on the Penn/Camden lines would probably be alright but only DC and Baltimore have much if any public transportation associated with the commute. I'd figure out who needs to be more available to their work, and who has more flexibility and plan around that.