Interesting observations, here are my thoughts ...
I agree that he had a weak constitution from childhood and had malaria several times and almost died from it. He probably kept himself alive a lot longer using his Liver Flushes and cleanses.
There is always a danger with cleansing and overloading the body with too many toxins at once, which can lead to a lot of problems and even death.
I strongly disagree with Weston Price's teaching. Dairy products are mucus-forming and cause disease IMO. But I do agree that a lot of vegans are unhealthy.
I know that Andreas didn't believe in taking anti- parasite herbs, which I think are absolutely necessary.
The only way we'll find out whether we're right or not is by our own health and longevity (or lack thereof). Health "gurus" don't have all the answers and you're right, we'll probably never know exactly what happened.