Crushed in DC is a great shop, most of my favorites in NOVA closed but Fairfax Surf Shop is still around. Alpine Ski Shop also carries some skate shit. I never liked either one much but hey it's something. For NOVA parks Wakefield was always my go-to growing up, Powhattan Springs skatepark in Arlington is solid. Duke Street park sucks but it's there. There are a couple further out too, like Lake Fairfax park in Reston. I haven't been up on spots around there in a while but the locals at wakefield/powhattan could help you out for sure. For parks in DC there's the Maloof park near RFK stadium, what's left of the bridge spot DIY in capitol hill (not much unfortunately), then some in Maryland like Takoma Park, Woodside, and Mount Ranier all in Maryland. There's also a little bowl behind Union Market. For street spots like obviously Pulaski, there's a bunch clustered around there downtown. Malcolm X park fountains, Welfare banks, Meade memorial, Archives ledges, United Transportation Union curb...there's a ton. Some more of a bust than others obviously.
Also I've never had a problem with mob even in the humid ass summer, maybe don't grip your board outside though if you can avoid it.