The time in which Richard Wagner was with his uncle Adolph and aunt Friederike in Leipzig was in 1822, not in 1823, as suggested in the movie as by that time he lived in Dresden.
Wagner's opera Rienzi didn't premiere until he arrived in Dresden in 1842, not in Paris, as suggested in the movie. However it is inspired by the art of the Grand Opera of Giacomo Meyerbeer.
Cantor Christian Theodor Weinlig's name is written in the movie as "Weinlich".
While it is true that Wagner wrote "The Flying Dutchman" on the way to Paris and played portions of it, it didn't premiere until 1843 in Dresden.
The signalment about Richard Wagner from the 18th May 1849 describes him as a man of an age of 37-38. On that day Wagner was actually 35, soon to become 36 on the 22nd May.
Wagner received the information about the performance of "Rienzi" in Dresden in Spring 1842. The letter from his brother-in-law Friedrich Brockhaus has the time "26th February 1842".