I am positive that some severely obsessed dude, whose identity I am certain of, has managed to hack into my mother's and sister's accounts to read my emails to them (which either never arrive or arrive open before they've actually read them) somehow also has access to at least the titles of my (several) email accounts and to my activity log on facebook, amazon and other sites.
He's also managed to do weird things like remotely getting my current housemate to subscribe to his best friend's facebook profile, for instance - if this doesn't sound too clear, her fb wall shows she subscribed to his best friend's fb profile in March, which she never did, nor does she recall ever receiving or accepting an invitation to become friends with him. He seems to still be enabled to follow my visits on the internet in spite of my 'clearing' of cookies, and there's a chance he might be reading this.
I have strong suspicions that he has also managed to hack into my work computer after an unexplainable series of emails and documents disappearing unexplainably (now this certainly doesn't tend to happen to me, and definitely not on the scale it recently has).
He is an IT professional and his computer knowledge is obviously more advanced to that of most people.
My initial questions are, what tools/means allow him to do what I mention above, is there a way (other than paying a computer specs to do it) to identify the computer from which he is doing this so I can get some tangible evidence, and what would you advise, technically speaking, in the meantime?