I'm not an expert by any means on this funding but I think the big thing you are missing is what is referred to as maintenance of effort funding which already exists and brings the needed NEW revenue way down. From this great article https://www.peoplespolicyproject.org/2019/10/30/how-to-approach-medicare-for-all-financing/ "The first thing you do is bring in existing spending on Federal Health Programs and State Health Programs, the latter through a maintenance of effort requirement. That gets you $1.761 trillion.

Then you can assume that Other Private ($0.308 trillion) remains the same, getting you to $2.069 trillion."

Sorry that I also linked Bernie's old financing document, the 2019 one is here https://www.sanders.senate.gov/download/medicare-for-all-2019-financing?id=860FD1B9-3E8A-4ADD-8C1F-0DEDC8D45BC1&download=1&inline=file

You seem to like reading about this so I would also recommend this article https://www.commondreams.org/news/2019/11/20/top-economist-robert-pollin-answers-key-questions-emerging-divide-between-sanders where he proposes a sales tax to fund Medicare for All which is interesting.

Now the problem with a public option is obvious and Rep Jayapal lays it out well here https://twitter.com/RepJayapal/status/1197702718967746565 I don't know what is going on behind the scenes which has her speaking the truth here but then also constantly defending Warren's public option but the facts remain the same

And never forget this about your boy Pete https://readsludge.com/2019/10/18/as-he-attacks-medicare-for-all-mayor-pete-gets-campaign-cash-from-health-care-executives/