Not to sound stupid, but I kind of see him acting like in the "Girls Lie Too" video, just showing his girl around, giving her his best dresses he plundered, rescuing her relation from choking, wrapping her up in a towel and taking her to bed, etc. I think he'd be a really sweet, flamboyant kind of lover, you know?
I dont have any problem imagining JACK tell LIZ he loves her....because IMO we've already sort of seen it (or a version of it)....right before the kiss we saw JACK stripped from the hard exterior he had BEFORE! we saw a really vunerable Jack there....so we've seen his sensitivity, we've seen him with his guard down....and we might just get a little something something from him in POTC3....i mean the man died! coming back from death...i can definately see JACK having an emotional breakdown (maybe not an obvious one, but one in his own little Jack way)