To get to the homework stealing, I just play and it usually happens within the first three weeks in game. Although maxing out his friendship points may actually harm this (I don't know if that event has prerequisites)
If you give in or refuse to tell on them when they steal your homework, they will be dom. If you tell on them/refuse to let them steal your homework they will be subby.
After they (try to) steal your homework, they will approach you and tell you to meet them in the media lab.
When visiting the media lab, eventually the harasser will ask for you to flash them, or to video you. After this eventually you will have a guest lecturer instead of the normal professor (If I remember correctly) and you will get the bathroom sex scene. This scene repeats a few times.
After this, he will find you and confront you when walking around campus during the day. I don't know if this is restricted to certain time of day, but seems fairly RNG (like the people stealing your clothes in the shower for the Best Friend story start). It's like the common toll event, but more rare and with harasser instead.
Then finally, there is one more event I know of back in the Media lab. But I haven't been able to find the prerequisite skill levels to trigger. Or maybe it's inclination based. I guess you could fiddle around in cheats menu to find out.
Like most storylines, it seems a bit random to trigger, and takes a while.