Not fundamental to what you are saying, but the "There is little evidence to support the view that Hitler received substantial financial support from big business" you quote is untrue. Big business, and also the upper classes, were more scared of the communists than of Hitler, and big business saw some nice opportunities.
See https://en.wikipedia.org/wiki/Secret_Meeting_of_20_February_1933 for Hitler's financing by big business.
"The Nazis won their support primarily from the lower middle class and the peasantry. These voters were strongly nationalistic in their political views and feared that the depression would deprive them of their standard of living." is also doubtful. The depression had already deprived them of their standard of living, and not just the lower middle class, but the whole middle class was a good source for Nazi votes. It wasn't all about nationalism, but also about jobs.
I will look into it. What I was researching was how the Nazi party first began to gain power and from the very beginning stages, it appears that
Reading this worries me because we may very well see street wars. As Trump's economic policies favor the billionaire class and more lower middle class white folks become unemployed, they will blame immigrants even more with egging on by Trump in this regard. It becomes a vicious cycle. Even if the economy tanks, he won't lose that population he won over in 2016: they will become more dedicated to him and the race wars will grow. Trump will stoke these fires.