No. The Support page that takes you through the “How can I unlink my Steam account?” query, doesn’t allow you to progress if you’ve linked more than 7 days ago. Which is pretty much everyone lol
I'm not sure. I tried a while ago to download the client from the official eso website and just manually logged it, it worked save for the fact that it didn't recognize that I owned morrowind so I couldn't go to vvardenfell