You are a lunatic because you are trying to do too much. He is despicable, forcing you to lift all those boxes. Too bad you didn't have a dump truck. Did you ask him and the cousin to help?
You have to stop doing this stuff. Don't do anything else related to him. If there is anymore of his stuff just throw it out. If he asks where it is say you don't know....you brought everything to his aunt's house that day. You need to get more passive-aggressive and less plain aggressive.
I doubt he and OW will be able to play that "we're so wonderful because we are teachers" card very well. Here in FL they are arresting teachers right and left for sex with students. It's not surprising to anyone that some teachers can be sexually perverted. And on that subject, how do you know that he and the BF and OW are not having a menage a trois?