Always interesting to see how people organize these things. Obviously, mine would look different from yours. Using your example, mine would probably look like this:
Album Artist: Ludwig van Beethoven
Album: Symphonies
Title: Symphony No. 1 in C Major, Op. 21 – 1. Adagio molto – Allegro con brio
Year: –
Artist: Ludwig van Beethoven
Composer: Ludwig van Beethoven
If Symphony No. 1 is the only work on the album, I would remove that part of the track title as well. But if there are more on a single disc, I would keep it.
Year is blank in this case, because this is a set that includes different works(?), so no composition/premiere date would be set. If it was just the Symphony No. 1, I would put 1801, since that is the publication date, according to Wikipedia.