i'm sorry this happened to you. i'm glad you were finally able to say no to him.
being obsessed over bathroom habits seems weird, i'm sure, but it sounds like this was just another way for him to be controlling. in the same category with controlling what someone wears, how their hair is cut or styled, where they go, what they eat, what they drink, what medicines they take, etc. it may also have provided an excuse to touch and or cause pain to private areas.
i was in an abusive relationship where i was not permitted to close the bathroom door. sometimes i was even supposed to use the toilet with that person sitting on my lap. which i couldn't do, which i got punished for, and which caused me pain and infections. i know this was just done to control one more aspect of my life, and because that person delighted in making me humiliated.
i'm glad you're out of that situation. thank you for sharing.