I think there are a lot of things we do know, at a 95% confidence level. Like people who have recovered and have IgG, very likely will have some immunity. Sure, there are exceptions (like me) who were taking immunosuppressives that screwed around with certain white cells. But I fail the antibody test.

Opening back up is going to consist of a lot of bets: Hopefully well-educated bets. Like don't go back to work facing the public unless you are recovered AND have an antibody test that shows you have enough IgG to be safe. That means we need titre tests, not just qualitative. Until we get there, isolation works. Mask wearing in public and maintaining distance works. Countries that have done just those two things have very few new cases.

Educating anyone benefits everyone.