I think 80% for heard immunity is a pretty high count.
IFR is a guess and yours could be right. It is lower than NYC but the developing world is much younger than the west so they might have a much lower IFR unless their lack of available health care hurts them too much.
Hopefully IFR will drop as well as we learn to protect the elderly better.
https://www.who.int/news-room/detail/14-12-2017-up-to-650-00...
Covid-19 should kill 30 million.
.5% * 80% * 7.8 billion.
That will be over many years however. Maybe 2-3 years.
Some estimates put Covid-19 at 10 years lost per person average.
If you can get it multiple times, which is likely after a few years, it'll keep killing forever but it'll slow down, and we might even slow it even more in the richer countries, like we sort of bother with the Flu for, if a vaccine is ever possible.
Currently China has an unsustainable model going (School is not back properly) for 1.4 billion. If however they can move to a sustainable model, maybe they might not get it..... Good luck everyone else.