That's interesting that you're not making much money, is the traffic all organic?
Tube sites are a bit harder to monetize but for PPC I also definitely recommend
Exoclick
They have pretty much every ad format under the sun and also pay pretty well and on time weekly via paypal.
CrakRev is also a great one to try if you have not already. They recently got a ton of new offers and a lot of their cam PPL programs convert extremely easy.
Best of luck!