Will say, as a former cutter, glad they took the knife, cutting doesn't do any good in the long run, it's a temporary escape that leaves marks that just aren't worth it in the long run. However, on the flip side, they took away the knife while also blocking you from a healthy outlet and your support, thank goodness you have the Ipod touch to access the forms. Your could try to do a system restore and see if that'll undo the site block, worse case would be a full restore, but you'd have to be sure to backup everything you don't want to lose from your harddrive, that will without a doubt undo that site block. it'll also wipe your harddrive clean and to factory settings, which is why you'd want to backup everything to disk beforehand. Then you can go into the parental controls and set them yourself with a password they don't know so they can't change them again. This is of course assuming it is your personal computer (EI: you paid for it or a gift thus putting it into your ownership). However, I do echo what others have said as well.
You're 18 according to your profile, moving out at that age can be scary, I did it at 17 myself so I know, but as scary as it is, it also gives you full freedom to live as you feel you need to live, with no one else being able to tell you "Well you can't wear this, you need to look like this, you can'ts access this." It's hard to live on your own at first, I won't even try to lie there, it is hard, but it is worth it for that freedom. Maybe you could talk to friends about possibly being roommates, that helps cut the costs a lot, if you're still in school then that can be a bit hard, but a part time job can help alleviate some of that strain, any legal income will help, it can be done, it'll take effort, it'll take falling and getting back up a few times, but it can be done, there's numerous people who have done it that prove it is not impossible. I suppose it's a question of how far you are willing to push, and how much you are willing to withstand for your happiness, it is doable, and it is worth it.