Everyone here seems to love telling you should never do business with friends. But based on what you’ve written, it seems like you’ve already learned that lesson the hard way, and all the commenters reiterating that doesn’t seem to be helpful at all.
What you need to do is apply serious pressure on this guy. You’ve said you are willing to lose this friend, so show him you are not fucking around. Call him and tell him in a very calm and collected manner that you are entirely fed up with the situation and you want out right now. You expect him to send you back all of your money immediately or you are taking him to small claims court. Do a little research and have some documents from the court ready to send over to him (even if it’s just a bluff for now). He will hem and haw and come up with every little excuse in the book. Again, calmly tell him you are not interested at all in anything he has to say. Pay up now or we can do it the hard way.
The only other good idea I saw here was the idea of undoing all the work you did somehow like re-coding everything and/or re-routing the URL. That will also give you some leverage. This is not over. The people telling you to just forget about $5000 are silly, but for the sake of a thought experiment, let’s use it to your advantage. The $5000 is gone but now you have an opportunity to earn $5000 with about what, 10 hours of work? Don’t take no for answer.
How many qualifiers do you need to present before considering maybe he’s not at all “going after” high school sophomores. Maybe he just went to a club like a normal 21 year old looking for girls in a totally normal and acceptable way.