As far as getting users, why are you coming to HN looking for users? You clearly read HN, you read about how to do PR and pitch, did you miss everything on how to find product market fit? Did you miss everything on research before building, or building MVP and getting friends to try your app?
I don't think you app is a bad idea, but it isn't something I'm going to jump on until I know other people are using it. If nobody is using it, their are no anon 'broadcasts' to be shared. You have a classic chicken-egg problem. Nobody is using your app, so their (likely) isn't any content their which is making people interested in viewing that content.
This is part of the problem with anon apps, where people can't try before installing. There is no point in me telling a friend, hey download this app because I'm in it, because... if I'm anonymous, they aren't going to see who I am anyway. What is your pitch to your friends as to why they should use this app? What do they say. Get 5 people you know to install and use it, then adjust based on feedback.