What are you hosted on right now?
shared, reseller or vps?
If indeed you do get those ddos attacks, its not only your website, but everyone hosted on the same server. Your host should do something about it.
my average transfer for 8 sites per 100k pageviews is 3.2gb // ~100gb/month
I'm on a VPS and have zero problems.
Look into a VPS solution instead of your dedicated.
Then again if you have a 30gb/100k pageviews ratio you must have lots of downloadable content. music/vids?
A large vps will probly not have enough space, and in that case, you have to go dedicated.
Now, remember that most (cheap) dedicated servers are unmanaged.
You get ddos'ed? You deal with it/fix it. The host will not do much about it.
Ah, and the last thing,
Did you ever receive a payment from advertising or you'r awating your first one?
Keep in mind it's mostly NET45 meaning you get paid 45days after the month finished.
So if you'r awaiting your october payment, it'll probly just come in the middle of december