I want to encourage you in all this and also suggest that Bucky thinks of himself, fairly literally, as a monster. We of course, behind the fourth wall, may enjoy his build but he knows he's basically an ogre - something big and strong that hurts people horribly. Maybe a lot of it revolves around the metal arm - he can barely stand to look at it and the thought of it actually touching Steve has the power to make him vomit.