Well, it is somewhat based on Klepper's novel, and Klepper did his research, poor guy. (You could blame the lack of gay on his writing in the late 1930s in a dicatorship with his time running out, but the two parter was made in 1980.)But yes, aside from that, it's pretty good sticking to the facts. The biggest "no way!" liberty I could see was Fritz playing flute in public while in Dresden without FW hitting the roof, but hey, FW is busy drinking with August.

(BTW, you can tell this is a West German movie made during the Cold War by the fact it can't use any original locations (including Potsdam, which was in GDR territory); whenever the action moves, we can a sketch of the relevant palace supposed to look like an ancient litography.)