Iceland has only tested 28,992 of its residents as April 6th, so that throws the rest of this conjecture out the window. (Although regardless the conjecture was probably not a great idea.)
I think the real point is that your original claim was a small sample that you were extrapolating wildly from turns out to be 10x smaller than you claimed.
Furthermore you are focusing on a tiny portion of available data instead of all that is available.
Given that New York State has 4,000+ deaths your "model" would indicate that 1MM residents have COVID-19? So if it rips through the remaining 19MM residents in the course of a few weeks the result will only be 80k deaths? And of course the healthcare system won't break down?
Also you said that the Diamond Princess only had a 20% infection rate but the Greg Mortimer is reporting a 60% infection rate. Seems like you've got a lot of facts wrong on the first pass, IDK.
It seems that 'all available' would diminish the signal of Iceland's good stat. What we really want is 'all good stats'. I think only South Korea is the other country with extensive testing.
According to my model NYC should only have a max of 13.5k deaths, without any mitigation.
Based on the Greg Mortimer stat, this bumps up to 41k for NYC.
It doesn't seem to pass just a basic level of consistency with present experience to believe that with no mitigation New York would only have 13.5k deaths when they already have 5.5k+ (and we know many more that have not and maybe will never be confirmed).
Even the idea of 41k at this point beggars belief, they are already well over capacity with some mitigation and the bodies are literally piling up.
I find it hard to wrap my head around the logic here.
My thought is since this is a new virus it will spread faster, and hit peak sooner. Also, those who are most affected are a small portion of the whole population, which will again imply faster time to peak.
It isn't about proportion of population, but whether they are only testing people already admitted at the hospital, which will drive the estimate up, or testing the wider population, driving the estimate down. SK is doing the latter through contact tracing.
Iceland may have the best statistic on their death rate from this virus, but these things are not static and depend on a zillion factors (slight exaggeration).
https://covid.is/data