Is raising one’s hand with thoughts of cursing – without uttering it – considered disbelief (kufr), or is it a sin that does not necessitate disbelief?

You have not committed disbelief by what you mentioned. Rather, it is proof of the soundness of your belief and your veneration of Allah Almighty. Allah has overlooked the whisperings of the self as long as they are not acted upon or spoken. Your dislike and aversion to these whisperings are a sign of the strength of your faith. As for Ibn Uthaymin's statement about reviling Allah with a gesture, it applies to a gesture that demeans the مقام (status) of Lordship, and not to your gesture, which was to ward off whisperings. Praise Allah for His protection and your salvation, turn to His obedience, and beware of anger.