1. Depends on what you mean by "Big". Big, as in I'm really into it, or Big, as in I'm very popular? I'm the former and not the latter.
2. LP stands for "Let's Play" so if it's something you play and you're giving commentary on it, it's an LP. So yeah, a live stream is a Let's Play so long as you're giving commentary. So if you can call what you're doing an LP, than by all means, start a thread! It would be even better if you have your livestreams recorded so people who missed the event can watch them later.