Some of ur theories are right but i dont think peeps should get worried if their partner tells them they love them  more than they normal did,sometimes it could jus be a realization of neglect on their path and they try to make up for it...In all i jus feel that the issue of ur partner cheating is a very sensitive one and can only b identified in ur own relationship,u know ur partner and u shld know wen he or she starts to act differently towards u...I say confront them