Just ask an admin to change b-day.
As far as you being under 18, honestly just wait. You've got school don't you? So get a good education and subsequently a good job. To pay for this stuff (I've probably spent a good $800 on airsoft alone in the past 3 months, which believe me isn't a small amount of money, thats excluding things like BDU's and stuff like that from when I was younger)
Also it's nice that you admit to your mistakes instead of digging yourself into a deeper hole so I see you being a good player in the future. There is one way around this though, which is if your parents get verified and play with you. I believe there was a person under the name hitarosu (or some variation of that) who did that and got his dad to play with him (I think he was 16 at the time).
EDIT: I did some looking into you and damn kid, you were an asshat back then I sincerely hope that you've matured like you say you have. Still it won't fly here, the rules have been set and we don't do case-by-case, we paint everything with one brush.