To all honesty taking in consideration what kind of awful vile degrading things he says to you and how horribly he behave with you (slapping you etc) it’s only understandable that you snapped and said things or he assumed you said those things (like called him fat whrn yiu did not ).

He says you are dumb and worthless, should you really worry that he maybe thought that you maybe meant he is fat?

As about cheating. If you aren’t a couple I am not sure what you mean. You’ve only met him once and that one time he treated you horribly (slapping you and throwing stuff at you). If you only saw this person once it’s not really a relationship so how can you possibly cheat on him? You were talking to someone online, someone who wasn’t even nice. It isn’t really a relationship

Are you trying to minimize abuse you endure by saying it’s yoor own fault? When do you start seeing a therapist?