fyi... there is no such thing as "unlimited" anything when it comes to servers

I'd look at getting a better host, you shouldn't pass 1 or even 2, and nowhere near 30!!
What are your server specks?
CPU, RAM etc..
Ps.. these are your stats
Threads
6,659
Posts
147,995
Members
720
and you get 400 on at ONE time?
sorry, but I don't really believe that
what is your session timeout set to?