I don't have nearly as much traffic as you do, but I have been making money with adbrite.
The first thing you need to do is kill the automatic approved ads. They are usually good for bringing in the lowest bids, and ads that have to be clicked through.
Instead, manually approve the ads. Look for the highest paying ads that fit your areas demographic. This will allow you to get only views from the areas you get traffic. Also, with your traffic, you should ditch the click ads, and get only CPM ads.
If you get decent click throughs, this should be enough to keep your ads up and running.
Selling ads is a good idea as well, but I would try to optimize adbrite first.