ISP means very little compared to being able to provide the first ever password set on it.
Password > anything - Even subscription details. All i can suggest is in the recovery form adding in one of the following ISP's; Comcast, Roadrunner, AOL.
You may be able to get the account back but it's keeping control of it that's the problem. If you're that pissed at him and convinced it's a lost cause, try recovering it and then get it banned. That'd stir some shit.
Do you have the guys IP in a screenshot from when you first logged on ? If so, and you're willing to spend some time getting your cash back go to
http://www.ic3.gov/default.aspx - I'm really not sure what you could say to them in your form but what he did is classed under fraud/theft. (I wouldn't suggest this if you're not up-to-date on anything law based)
If you need any advice or such drop me a pm.