I never streamed videos using Django/Python, but I have some experience in the field of streaming video in frontend apps. I can certainly not answer all your questions. In my experience it does not really matter where the video is hosted, a CDN is fine if you want to distribute the video world-wide. I personally think you should start with the question on how you want to play the video in the browser. Choose an appropriate video player (could be html5 video) and you have an idea of what is possible to play and what not.
3) The format matters depending on how you want to stream the video. Progressive download (e.g. mp4)? Live streaming (unprogressive, e.g. HLS)? You can find example videos online and test if your video player can play the videos on the platform you want to support.
7) As said, you need to check out which player to use in this case. HTML5 video is not widely supported enough yet in my opinion, but can play most formats in the most modern browsers (Chrome, Safari).
Hope that helps.