I know I have to work on those sixths, any hints/tips?
I practice such things in the following manner: first I try to play the sixth in a very slow tempo and very eve (perhaps with metronome), until they are very accurately together. Than I accelerate the tempo step by step, not becoming faster, until a certain tempo is accurately played. I do this up to the tempo, I wish for the piece. Sometimes I practice them rhythmically (f.ex. as dotted or double dotted rhythm or as triplets. I develop own sixth-exercises, which contain the passage of the piece and which I can practice in an "endless repeat". It´s important to stay always in a certain eve beat and not to interrupt for a while.
As far as the tempo goes, I've seen this particular piece played at a wide range of tempos, I will try a little faster though.
Yes, the tempo is a matter of taste, indeed, and my suggestion to play it a bit faster is absolutely subjective. "Allegro moderato" is not an exact metronome-prescription, but has a certain variety of basic beats. (You can find them on the metronome-scale, as you probably know.)