What you need to do is figure out the burn rate to sustain your family, figure out your safe withdrawal rate (e.g. 3.5%), then you can easily get amount of capital required.
A Mormon friend of mine, with 5 kids, spends less on food for his family than we do (family of 4) --he/his wife are just much better at spending on it. There are also factors like, it's possible to get a 3-4K sqft house for a very reasonable price & low taxes, vs. living in a tiny box in San Fransisco for 2x more.
Those historical returns are ridiculously optimistic. In fact stocks aren't great once you look globally. Imagine investing starting from 1900 Germany or Russia. In both cases you would be zeroed out. It's a form of survivorship bias to look at American stock markets only.
I think a 0% after-inflation return for a normal investor (ie. no specialized domain knowledge, no insider info) over the next several decades is already mildly optimistic.
