Rather than monetize, I think instead you should try to get more people to install it. Make it better. Add features to block ads or something. Clearly you've built something people want. Find a way to engage with your users and build more trust with them. Your next app will be quite popular with them, I'm sure.

You're trying to monetize too early. Get real traction first. A million dollars isn't cool. You know what's cool? A billion dollars.