Block them on psn?
Do not missunderstand me, I am genuine curious how they are harrasing you.
You have a serious problem that I just can not fathom.
So my questions and ponderings are not in the form of "omg, who cares, just ignore and go", but more of a " I do not understand, please enlighten me if you can".
Now, I understand that you got enough on your plate, so if you do not wish to explain a stupid person like me how all of this works, that is cool by me.

Why is someone sitting afk in your house a problem?
Is it not possible to lock the house? (I do not own a house, so no idea).
Do you not spend a lot of time in instances where they can not follow you?
Have you tried to get mobs to aggro them and watch them die over and over again?
Is switching servers not feastable? Or starting on a new account?