Maybe you can show interstitial ads once per app session after 3-5 random button clicks. My CTR drop to 3-5% compare to existing 7-9% after remove interstitial on app load.
Regarding the loading slow, I suspect eclipse is the root cause. Eclipse is loaded with a lot of features that are not really necessary for normal native app. I switch to Android Studio and find it very easy to use and quite fast. But it depends on what you want to achieve also.