For sims, try an e-sim if you phone supports it: https://www.tripzilla.com/esim-travel-united-states/135697.

Highly recommend the smithsonian museums, including natural history museum, native american, and Hirshorn modern art museum. All smithsonians are free.

Expect 70 degrees over 50 degrees, so chilly enough for a coat at night.

I wouldn't go so far as Baltimore for an aquarium. You could always go to the National Zoo!