What are typical Click2Install rates on Ad Networks?

This conversion rate is definitely very low. Check the integration to make sure clicks and sessions are firing properly. After that, check your app page to make sure there's nothing that would turn your customers away from installing.

Unity is generally a good network, but it's also possible something weird is happening with impressions and click measurement.

Hello There! I'm not sure if the question is still relevant for you, but your CTR doesn't look too bad. However your CVR seems really low. Assuming these are numbers from your Unity dashboard; I would double check your MMP connection to make sure everything is firing correctly. If everything is okay with your MMP, a second step would be to check your App Store Optimization.

For future reference, it would be easier to monitor your IPMs directly with video networks since the click through rates tend to be very inflated on these channels; although Unity is an exception here.