The LAA Admirals Club around B30 has showers and lobster rolls (for purchase, may be seasonal though). A little far from where you're likely landing coming in from DCA but you can stay airside in the B terminal. There's a LUS Admirals Club closer to the low number B gates.

You'll have to go landside to get to E and then reclear security. JL doesn't participate in PreCheck. You can either walk (long way around or possible confusing walk through the central parking area) or take the airport shuttle through the loop.