Dear R' Avi,
I listened to your shiur on parshat shemot on my walk to work today and enjoyed it, as usual. Most of the historical analogies you invoked made sense and all your larger points definitely stand, but there are a few details that were slightly off although they don't have a bearing on your overall message and to understanding the Ramban.
1. Kristallnacht was organized by the Nazis. It is not really accurate to say that it was a sort of spontaneous night of violence, even one prepared by the marginalization and demonization of Jews. Kristallnacht was indeed a turning point but it wasn't a situation of "the people" taking matters into their own hands and the government sitting back. Kristallnacht had the blessing of Hitler and was spearheaded by Goebbels, Minister of Propaganda. Regional and local Nazi Party leaders then coordinated the violence in towns and cities. The people who carried out the "pogrom" were devoted members of the Nazi Party, mostly members of the SA (storm troopers) paramilitary groups. They destroyed shuls, Jewish stores, and private property, by setting them on fire and breaking the windows and defacing interiors. Many Jews were also beaten, some killed, and some interned in concentration camps (not death camps, which were only built several years later) - they were usually released after a few days. All of these details show the extent of state/Nazi Party coordination (the two were not identical but existed somewhat in parallel).
Some ordinary Germans (i.e., not Nazi Party activists) participated but relatively small numbers. Police departments and fire departments were told of the planned riots an hour before they began and they were instructed to back off but to prevent looting by people after the pogrom. In some places, police and fire departments did intervene; often, when a fire started, the businesses or homes of non-Jews were also threatened, and the firefighters or police could use that later as justification for intervening.
As a whole, the German public was not crazy about the events - it was really something carried out by the young, hardcore Nazi militants. The Nazis wanted to portray Kristallnacht as a spontaneous eruption of outrage against the Jews, but very few people bought this domestically, as Nazi intelligence reports indicated afterward.
2. The scenario you invoke of people killing with impunity (as the Ramban describes the killing of Jewish boys) and then the authorities not doing anything was not the way things happened in Germany itself. That kind of situation is what you got in Nazi-occupied Ukraine or sometimes in Poland in areas where the Soviet Union had just withdrawn and the Nazis were about to arrive. In those places, the Nazis could rely on massive civilian involvement in genocide. But on the whole, they preferred more organized means. First, mass shootings and eventually deportations to death camps.
3. The "Final Solution" was most likely formulated only in late 1941, after the invasion of the Soviet Union. That is to say, the plan to kill all Jews in Europe (and beyond that) was only articulated then. The Nazis initially aimed at the removal of Jews from Germany and Austria through deportation. A few historians believe that Hitler had decided on and directed the implementation of genocide already in early 1941, but almost no one would say that this was the plan from the very beginning.
4. Your description of the 1933-1938 period and the various measures taken to both marginalize Jews economically and socially (e.g., by dismissal from the civil service and from the bar) were really good and important. Those measures did eventually make it possible for people to see it as acceptable that German Jews, citizens of the country, could later be "deported" eastward but in themselves these were not sufficient causes. What made that kind of genocidal program possible logistically and psychologically was the world war, begun by the Nazis in 1939. And probably, it could not have happened and been maintained without the invasion of the Soviet Union and the kind of warfare that then took place on the eastern front (extremely brutal and radicalizing for both soldiers as well as the German homefront, not to mention the civilian populations that came under Nazi occupation).
Anyway, you probably know most of this and obviously for the purposes of the shiur, all this information is completely unnecessary. But in case you are interested and want a quick read through, I am sending you my Powerpoint slides of the two lectures I gave in my modern Jewish history course this past semester. They present an overarching analysis as well as some of the important details. The slides have brief point-form notes on the bottom (in the "notes" view). You'd probably have to download and open in Powerpoint to see those. I am teaching a course on the Shoah next semester.