In a sense, you're brokering AdSense ads? Is this even legal? Can you provide some form of screenshot of documentation from Google that allows you to do this?

And for you to be making 30% as your cut is extremely high... You shouldn't be making more than 5-10%, to be honest, or you won't get the masses using your service. Maybe a 75% to your users, and 15-20% reserved for referral commissions.