Thank you for this very excellent summary of the current status of this discussion. Really a wonderful article.

Two comments:

1. In the third to last paragraph, you may want to again clarify that the 20B number is referring only to the Milky Way galaxy.

2. I am surprised when you say that it is not important for the star to be a singlet star, and that it is not important that the star be close to the galaxy center (or not). While I'm sure there are many cases where the planet would experience stable conditions over long time periods even close to the galaxy center, or even within a multi star system, in general, I would anticipate too much instability/too many upset conditions.