Travel to around about 1579S, 993W on the world map, then manually run south until you find a river. Follow the riverbank south and east; after a few minutes of running you'll notice a few trees, and the bridge is right there amongst them. Cross it and you can continue on south to Caladon.

I haven't experimented with this a lot myself, but my attempts failed to make Willoughsby appear in Tarant early, as just the act of entering Qintarra or Caladon didn't trigger it. I concluded that his appearance was probably associated with reaching a given point in the main quest, and therefore things like recruiting Perriman Smythe or Sebastian or training to mastery in persuasion were impossible by short circuiting the game. Have you had better luck in getting Willoughsby to activate?