If he's knighted he takes a secret vow of celibacy, so it's all over.

Just kidding.
Most romances in the game seem to have some uncomfortably long pauses between romance bits. One thing you can do is pause the game and walk away for several hours. I believe the romance lines trigger on real time and not game so if the game is paused the romance clock is actually still ticking. Anyway, I wouldn't worry about the romance ending. As long as you don't snub him (meaning choice 3) in the romance dialogues and boot him out of the party, things should eventually progress. You could also use shadowkeeper, to check the global variables on the romance.