I had a good read of your description and would like to add a few pointers. You suggested those 3 ad networks, which is all well and good, especially as you have chosen to steer clear of iAds (very low CPM).
If, like me, you have developed using Unity3D then I suggest you take a look at the Unity Ad networks, possibly rewarding players through an incentivized system.
Also, I suggest that you look at startapp as the CPM for that is also very high. Also, the returns for admob are quite low in recent years, so I'd also avoid that.