Thanks, I'll try the Frame Saver (and I'm also considering using another chem to remove/convert the existing rust).

As to the lock, I was thinking about getting a OnGuard Bulldog Mini TC U-lock (or the Pitbull Mini) and putting it through the rear wheel rim & tire, inside the triangle as described here, and then also getting a cable lock for front wheel, seat, etc (not sure which cable lock yet though).