Does installing and re-installing my own app affect my app's rating/ranking?
As far as I know, this should in no affect your app's rating. This is something I do myself constantly with testing of my own apps.

The only thing that will ultimately affect your rating are the number of stars your users give you. Yes, you can rate your own app, but you can only do it once. Uninstalling/re-installing shouldn't change your own rating to your own app either.