Do you think Jamie would ever have told Claire how be felt about her if they hadn't been forced to marry? And why do you think he didn't try anything with her? He says himself that he'd kissed and courted other women before, so why do you think he was so reserved with Claire? :)
1. Yes, Jamie would have eventually told Claire even if they hadn’t been forced to marry. Jamie would have still looked for any opportunity to keep Claire safe. And I think he would have come up with the idea to marry Claire on his own - though he wouldn’t have told her his feelings right away, because he never would have wanted to pressure her into feeling the same way.
2. Jamie didn’t try anything with Claire because he profoundly respects her. Sees her as a whole person. Is very sensitive to who she is, and what she wants (and doesn’t want). He knew he would have to court her, to gain her trust, because nothing would easily sway her. Unlike just about every other woman of his acquaintance, Claire could take care of herself and wasn’t afraid of men. Therefore, Jamie’s approach with her had to be very, very different than with other women. So he’s a bit shy and tongue-tied around her – not the brash, confident young man Annalise de Marillac says he was.
Also - he knows that had he made an advance at her, and she didn’t want it - she’d probably geld him.