If I were in your position, while I wouldn't look to get on the W&OD, I'd still ride on the Virginia side to the Custis (or at least check that out as a possibility at some point). The distance would be almost identical if I understand your start point right (to up to a mile more depending on exactly where you start), and you could get over to Old Dominion Drive or the equivalent, keep going till you cross Lee highway and ride parallel to Lee until you hit Custis around the Lee shops (top of Spout run with Italian Store, Big Wheel Bikes, etc.) Then take the trail not to Key bridge, but keep going to the bridge that takes you straight to the Mall. That is more street, rather than trail, admittedly. But it avoids the rough towpath and the Chain Bridge.
My tires on my main commuting bike are 32s, and I don't have any trouble riding the towpath with my son on leisure rides, but I admit I haven't commuted on it, but I wouldn't be adverse to doing so if it made sense. I wouldn't generally want to go super fast on it (I mean fast for me and my bike, which isn't really super fast). It probably helps that I have Brooks Champion Flyer saddle (sprung). So, it sounds like that route is getting comfortable for you and makes some sense, but it's far enough out that there are lots of options.
Last edited by yoder; 10-06-10 at 02:03 PM.