My daughter's school has 2000 kids. 4000 parents. In Santa Clara county the death rate for 40-60 is .5% [1] That would mean 20 parents dead if everyone gets it. Many of the households in immigrant families are multi generational. That will have a multiplying effect.
While it's still going to be a very real number, I think you are overestimating the number of deaths considerably. I appreciate that you provided a link, but I don't think that source includes the information you would need to make the estimate you are looking for.
First, I think that you are implicitly assuming that there are an equal number of people in each age category. In addition to the percentages you quote, you also need to know the percentage of the population per age range. Second, the "case" rate is the not the same as the "infection" rate, as it only includes confirmed cases. It's usually assumed that for each confirmed case, there is some unknown multiple of this number of infected individuals.
Eyeballing the chart here (and realizing that Santa Clara might not match these numbers, and guessing equal number in the relevant 5 year age ranges) a better estimate of the death rate for the 40-60 year old group is probably something around .15%: https://www.acsh.org/news/2020/11/18/covid-infection-fatalit...
I simply did percent_dead times num_dead/percent_cases times num_cases. That leads to ~0.5%. I agree with you that IFR is unknowable without very thorough sero-survey. So all we have is CFR to go on. The ratio depends on population age and test availability etc.
This is a great thread [1] that goes through the IFR estimation and relative risk of dying due to COVID for various age groups. Bad news for me (45-54 age group) my risk of dying goes up to 1.7x if I get covid.
[1] 12.7% deaths and 29.1% cases https://www.sccgov.org/sites/covid19/Pages/dashboard-demogra...