I make this trip quite a bit, and will be just a day ahead of you. Lately, I think that 81 is no better than 95 and can often place you in winter weather this time of year due to elevation etc.
Rte. 95 has gotten much better. Not sure how far you are going, or which direction, but also avoid the George Washington bridge in NYC. It is horrible, as is the Cross Bronx expressway that you will find yourself on. Use the Tappen Zee bridge north of the city.
So, the only issue is traveling with propane through Baltimore...you can't use the tunnel. The route to take is 695, over the John Phillip Sousa bridge.
I have always used 95 from Baltimore to DC. There is a 295 from Baltimore to Washington...but I don't know anything about it.
Around DC is not an issue, take the outer loop...just follow the 495 signs. As a general statement, it is best to avoid rush hour in either of these places.
Safe travels!
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