1) The HAZMAT reference was hyperbole for effect, I know, but the infectious disease folks (who do this as their life's work every single day) adjudge that mask wearing is a basic and essential mitigation step...they're available to everyone at very little cost and the "intrusion factor" (my term) is minimal...face shields obviously help and are welcomed, but problematic when it comes to "mandating".
2) I'm guessing you posted that 40K deaths figure because you know that's right in the range for yearly 'Seasonal Flu' fatalities, per the CDC...and you raise a fair question...it's a judgement call, for sure, as to how we view and react to health issues. In our COVID-19 case, the infection rate and virulence level is literally overwhelming hospitals right mow...to the best of my knowledge this has never happened with Seasonal Flu, plus the death toll is rising sharply to a current total around 230,000, with three more months to go for an annual measure. BTW, in my travels to the Far East it was not at all uncommon to see random citizens walking around all times of the year with masks on, so other societies don't find mask wearing to be an "imposition".
3) That's an even better question, and one that we'll all be anxious to know once the vaccine(s) get here. It's possible that the Seasonal Flu example could be a guide, but in any event, since non of us quite understand the micro-biology or epidemiology of this pathogen, we'll just have to wait and find out. Fortunately, even our most knowledgable pros are optimistic about "normalcy" in 2021.
P.S. The link is not so much for you, as we've already discussed "R0", etc...it's for others who might stumble upon this post.
Link: https://www.news-medical.net/health/What-is-R0.aspx