Let's see if I can help:
#1: You have to go to the "info and homepage" tab in the publication's menu. At the very bottom of the page, you can search the writer's names and add them.
#2: Private Messages: On a writer's story, you can highlight their text, and a menu will pop up. The button on the far right of that menu will allow you to leave a private message.
#3: I'm actually writing a story about this topic, sharing many hidden insights into the matter. I will publish it on either Monday or Tuesday.
#4: Highlights and claps are more than a vanity/feel-good metric. A high level of highlights and claps trigger the Medium algorithms for further consideration by Medium Editors. It is how a story gains an opportunity to become viral.
#5: That was the frustration I experienced. I spent an excessive amount of time trying to get into well-known pubs with no success. Moreover, I never received a response to my stories or emails to the Editors. This experience is why I started FW, so I'm grateful it happened.
I hope this helps. Thanks for the awesome read!