Others have already chimed in, but in your position, I would live in Mt. Vernon in Baltimore, especially if you are both taking public transit or you are driving and your partner is taking public transit.

That way your partner can be close to the train station and you can be close to work. That said, if you are both willing to drive, that would open up a ton more options on where to live.

Union Station is pretty close to Capitol Hill so he can walk to work once he gets off the train (within reason of course).