Though there is a substantial amount of metre changing throughout, the length of the quaver should remain constant at 304 beats per minute (320 in the final Presto). This will help in driving the dance ever-forward. However, when the rhythmic chains are broken in the middle section, the music should ebb and flow, the emphasis here being on song rather than dance.
Difficulty level, roughly compared to ABRSM exam grades. 0 is beginner, 9 is advanced (beyond grade 8).