No, you got confused:
The piece he plays in the house for the Nazi officer is the first Ballade in G minor, Op. 23.
The piece he plays with the orchestra at the end is the Polonaise. And it is, indeed, a "real" piece for piano and orchestra.
Definitely try some other composers. If you like Chopin, chances are you'll like the Brahms piano pieces in the later opus numbers (76, 116, 118, 119), or maybe some Schumann. Rachmaninoff's shorter works (op. 3) may interest you as well. If you're feeling adventurous (and a tad suicidal), check out the Brahms sonatas.