The way I avoided "dead subs" is by not doing any sub for sub or crap like that, than all your viewers will only subscribe because they like your videos
It might not be you, but youtube. Youtube has been "broken" for a while now. It might not send your subscribers your videos in their sub-box, so they will unsubscribe because it seems you are not uploading
720 60fps because 1080 30fps does have a good resolution, but i would prefer smoother frames over resolution. Also note that some people's computer doesn't go up to 1080p
I feel webcams are good for horror games or try not to laugh challenges, but other times it just takes away from the gameplay and distracts your audience.