Thank you, Max, for an excellent analysis. This is the kind of thing that UBI advocates should be doing more of — not just talk about the many attractive features of the UBI concept, but also about how to make it work.
You might be interested to see my own recent analysis, “How Much Basic Income Can We Afford?” It takes the same approach you did — sources and uses of funds, revenue neutrality, etc. I posted it just yesterday over at Medium’s Basic Income publication: https://medium.com/basic-income/how-much-basic-income-can-we-afford-52cc8e9da65