1. Well, it's not exactly a junta (but very much army-dominated), but yes, the Civic-Military Regime does last until 1984.
2. The Kaiser is killed during the violence in Berlin, and his son is much less liberal-minded than he is, so he goes along with the army's diktats and helps cement the new autocracy.
The United States actually isn't going to join the war, but instead get very rich from selling arms to Britain and France.
Germany's not going to be anti-semitic. They've won the war, Britain's drifting away from the continent and both France and Austria-Hungary have been crushed.
And there's no WW2, just a long series of proxy wars between the US/Britain and Germany/Russia.
TTL's Germany can't be put into any one ideological box. It has a very robust, almost socialist welfare system, but is hostile to unions and favorable to large corporations. Maybe quasi-Fascist, but it's a mixture of OTL imperial Germany and regimes like Japan and (as you mentioned) Spain.