Also you have to use a native app for Netflix and if they wanted to, they could also stop supporting Amazon devices at any time. There wouldn't even be a work-around thanks to EME.
The YouTube TV service doesn't use EME, no. And isn't terribly relevant to this thread either.
2. I firmly believe now that EME is standard YouTube will start using it, especially as they start rejecting independent creators in favor of more High Budget Commerical Creators and Tradional media whom they already show a preference for. These Companies will demand it just like the big Movie Studios
3. I am not subscribed to YouTube TV service so I can not confirm but do you have a source or technical document showing they do not. I would be shocked if they were allowed to get Commercial deals to carry main stream cable channels and stream then in the clear with no copy protection.