the Main character is made to promise not to tell the sister (by the g/f) about the jerk and that in there is a quandary... do you break that promise or find something else to do.
Yes, he made a promise but in my native language we have a saying which roughly translates into 'emergency breaks the law' meaning you can break laws/promises in very exceptional cases.
A simplified example: when a kid is badly hurt and the parent is driving to the hospital, how much attention will said parent pay to the speed limits at that time.
This logic applies here due to the exceptional circumstances of her condition. Again details about the molestation can be left out to not completely break the promise, but the sister needs to know about the stalker for safe-guarding the GF.
And my point stands, she made a video on her first day home and he made a map as preparation for the mornings.
I would think this morning preparation package would get regular updates once you gain more experience or significant things happen in life, like this sexual predator.
There is only so much you can do to protect someone from another without imprisoning them somewhere and not letting them interact with the outside world.
The GF is interacting with the outside world (shopping, restaurant 2x, the park, strip club, swimming), just due to her condition, never alone.
And due to her condition, she should not grow tired of being constantly escorted because it is always new to her.