X2 on avoiding Wash/Balt. The stupid tunnel doesn't allow hazmats, and our propane tanks are considered that...so...it's just a plain pain. When ive done it in the past, i take the francis scott key bridge around baltimore. Plus the traffic is tight, aggressive, and hard to maneuver thru without "white knuckling" it.
Since I'm in PA, I take route 78 west to route 81 south all the way down to VA/NC then try to cut back over to 95. It only adds 25 minutes to my trip and is way worth it.
As for dewinterize, I wait until I get to warmer temps to do it, since it only takes a few minutes (turn on water and run it for a bit). Usually it's warm enough in NC or SC.