I do support underage gambling. My parents wish all I was doing was gambling when I was 16.

I can't even remember my last two years of highschool. I think that was my LSD period....but I could be wrong.
What should you do? Get your dad to open you an account with $25 and play super low stakes until you get old enough to hit the casino and then give up online poker and move on to reality. If dad won't open you an account, find a friend that has an account and give him $25 cash for a transfer. Be creative...you're 16. You must have a million ways to get things 16 year olds aren't supposed to have.
As for proper poker....I agree with everyone here that playing a freeroll with a buch of crazy shove-addicts won't ruin your game. But I don't think it will help your game grow very much. You'll never see that kind of crazy shoving in a real life tournament or in an online tournament at higher stakes. You may run into that kind of player in real life, but usually it is one guy at your table, and beating one crazy shove addict is totally different from swimming with a table full of them.
And if you want to play "proper poker" as you put it, get some books and read them for cryin out loud. I have to tell you that the youngest players I play with, the guys with the backwards caps who still shave only once a week and live in their parents basement, are the second worst group of live players I see. Most players that are weak on theory at least have years of experience to back them up, but young players are weak on theory and have no experience to draw from.
You can leap ahead years in your game if you do enough reading.
Good luck