Does he like prune cake? Have you recorded the wretched screams for contribution to a sound-effects library?
About the toilet cleaning, I'd take the direct approach. You know that four-part escalating communication tool, right? Neutral observation -> description of effect on you --> request --> consequences. Or something like that.
BF (quirky NT) had been single without roommates for a LONG time before I started sniffing around. His toilet technique involved letting marks disappear with repeated flushing; his toilet "brush" was one of those gizmos with replaceable cleaning-goop-saturated pads.
"I noticed that your toilet bowl is prone to collecting skid marks."
(For the effect bit, I stammered something about finding it unappetizing.)
"Could we try using the gizmo as a brush, even when the cleaning-goop is depleted?"
I never got to the consequences step; if BF had been a jerk about it, I wouldn't have continued seeing him, but I also wouldn't have drawn that connection overtly. A flatmate who's not hoping to get into your pants will likely require a more fervent conversion effort.