I think you can definitely do better… You are making only around 2 cents per click… Some people say CPC’s might be irrelevant these days given the number of CPI campaigns… But for US and that too from millennial I think they should be higher… One good way to judge your network would be to see how many different campaigns you are getting when you open the app couple of times both on wifi as well as on your carrier. If they are mostly same, time to change…
Maybe you can add some other network on exit as well… Try mobfox… They seem to have decent inventory for US. You could also try startapp or appbrain to show the exit ad.
You can try them out if you dont have better options. You are right, they work better if it is a gaming app. The other option is to use mobfox and use their mediation platform to plugin other networks.
You can PM me your app details. I could give you more suggestions.