Right so I am doing this for a (pretty) valid reason. My friend that I have known for quite a while has been sexually abused by a person I also know
You need to treat this how it is, a crime, so plan this out as if you were about to rob him or beat him with a baseball bat. You know him, which makes this dangerous, and as long as you have hopefully followed the 3 rules of black hat club, which is
1.Shut the fuck up about black hat club
2.Shut the fuck up about black hat club
3.Shut the fuck up about black hat club
You should be fine to hack this bitch. But of course, you told your friend, and my guess is she probably told someone else(maybe even someone that would reach this bitch), if that is true, opsec is going to be risky. You also need to outline your goal, if he a psycho, so what? Are you going to press charges(with evidence you can't use in court because you committed a felony yourself), or ridicule him?(which isn't going to work because if he is actually a psycho or a sociopath, he will think everything is fine because he lacks a precursor to guilt, which is shame and worry). If you just want revenge, how are you going to show it? By straight telling him, "ha ha i haxxed ur shit niqqa x-DDD DD",which will make him remember the email he got and possible report you?
(put towel over the phone so my voice doesn't sound like usual. Will this work? Also hide caller id)
No. It won't work, put a towel over your phone and record it, if you RANDOMLY got this as a call, would you trust that person? If they sound like they are literally talking out of their ass through their pants, would you trust them?
Buying a domain for a short period of time is a bit risky, mainly because it keeps logs on something you can't reach, I would try to self host and maybe spoof it with SET or something, usually that could work on a LAN network, you go to school with him? Maybe even set it up at the girls house if he comes back.
In any case, I don't completely know what is going on, personally I would drop it, I'm not some crusader for good and valiant, but I'm also a dick,you could do some research on reporting abusive relationships since it seems like its gone a bit far.