As a large person myself, I can tell you this, It's going to be a long road to stardom. However, you have an advantage, us big kids are immune to pain because of our stature, there for, falling isn't as big of a deal. When I figured this out, I started getting better at park. Just convince yourself you are invincible to getting hurt. Spinning is going to be slower, that is inevitable. I finally learned to spin when I was 18, after 4 season of skiing constant park. Rail will be your best friend. Look at Eheath, he's a big dude, but he can still kill a rail. You're going to be three swapping, but people will be impressed when you can swap and spin off down rails.
But when it's all said and done, you will realize that big dudes aren't meant to be park rats. You will move out west and start skiing real mountain and real terrain, where the big men thrive. Skiing powder, gnarley chutes, and dropping fatty cliffs will be your calling, I guarentee it.