Oh, Leineweber's dissertation is great stuff! It provides several key bits of biographical information about Morgenstern, demonstrates pretty efficiently that 99% of his stories about young FW (and FW's relationships with his parents) are nonsense (with the F1 stuff for the most part indeed hailing from Fritz' "Histoire" as I guessed, including, btw, the "he married unnecessarily a third time" complaint) but that the stuff about older FW is far more reliable. Most intriguingly, he thinks the contradiction between Morgenstern claiming one thing (FW isn't cruel, FW is polite to ladies etc.) and then demonstrating another via the anecdotes he tells was entirely intentional on Morgenstern's part, with Morgenstern employing the "and Brutus is an honorable man" technique in Frederician Prussia.

A seperate, more detailed write up on Leineweber/Morgenstern to follow.