I can't imagine one person running over 300 forums with 275,000 active users. That gives you an average of eight minutes a week to tend to the needs of each one.
I used to run a single forum with 50,000 active users, and even putting 20 hours a week into it, I still didn't give it everything it needed.
I know someone currently running a forum with about 20,000 active users and it's a full-time job for him.
I don't understand how it's possible for one person to run 300 forums well.