Hey John, here's a quick answer to all your questions in the order you have asked.

1. The process shouldn't take more than a day. you should have received a mail saying you have joined the partner program. contact medium support if you haven't got it.

2. Once you become a partner you can put all your old articles behind a paywall. so don't worry.

3. Joining a publication is supposed to get you more views. But most often that's not the case. No one here really knows how views on medium work anymore. Try a mix of self publishing and submitting to other publications to see what works for you.

4. Most publications do not accept already published articles. Very few do. Searching for them will take a lot of time and the difference in your views will not be worth it. So just put your old articles behind a paywall (after you become a partner) and let them be self published. don't disturb them. Focus on submitting new articles to publications.

5. You can edit a piece even after publishing it in a publication. No issues . Just don't edit the same piece many times. And yes it still appears on your list.

6. unfortunately medium doesn't make it easy to discover publications. So you have to google "medium publications to write for". you will get a list publications suggested by other writers here. that is the only way to find publications now. Submit to the smaller publications first.

Hope this helped.cheers.