Can't comment on DC to bridge. But, I've ridden from just after the bridge to Fenwick. That's just about 100 miles if you take the heritage route (I think that's the name). I could be wrong on the name, but there's a few cue sheets floating around out there. Hardest part was crossing back over 50 after the bridge near the outlets. Other than that, they're fairly lightly traveled roads and you can pick and choose once you get closer to the shore, say around 113.
Holy moley, I just realized the age of the original post. Sorry for the useless bump.