I've gone through similar things, it's not easy to deal with and in the end only the person with the problem can decide if they're going to get better. I hope it works out for you and your friend. That stuff is never easy.
As far as the professor is concerned, I wouldn't mention what's been going on. If it's someone you're friendly with and want to mention what's been going on as a separate conversation, then ok.
But I wouldn't bring it up in the context of exams. For one thing, there may not be much he can do in the way of cutting you slack. Second, if he's going to be preparing you for real life/ a career, he's going to tell you that life isn't fair and important **** happens at the worst possible time. Your future employers aren't going to give two ***** what you've been doing in your off time, you still need to show up and work no matter what.
So just study as much as you can, then go in and take your exam. Asking for leeway or special consideration is going to get you nowhere in school or in a career. Remember there's always someone who's dealing with more **** than you are, and that person's going to show up and do what needs to be done, most likely without asking for special consideration.
Not trying to be cynical or a dick here, I've been in your situation and frankly you remind me of myself at that age. So do what you want with this advice, but I can tell you that in a career, most people won't care what you've got going on in your personal life, they'll just expect you to show up and do the job.
(wasn't totally killed, but has a very distinct rattle). I hit it with a 2000 watt power amp bridged, preamp cranked/ weird feed back mishap, because I wasn't paying close enough attention what the fvck I was doing, when firing everything up for the first time (alot of hands in sh1t, head under the hood hooking everything up). Made a very loud "Kick drum" sounding thunk and the cab jumped off the ground a bit. All said, one of those $200 lesson learned mistakes. 
