For "saddest" look at the second movement of Schubert's second last sonata in A major (D 959): Really difficult to find anything more desperate than that, and the middle section adds some madness to the despair. I would say the mood is (near) suicidal. Not to be recommended for individuals already prone to depression.
the ending music was him playing a slow movement of a schubert sonata i think... would anyone know which one it is?
B flat Major.