If you can't play it fast, it usually is just a matter of working it up to speed. You must make sure you playing it right slowly. Make sure you are staying very relaxed in that right hand, also give a slight accent to the downbeats and not to every note/chord. With the 6ths, again it's accents. When they first start, think "down" on the thumb then "up" with the 2-5, then later down w/ the 2-5 and up w/ the thumb. Practice at least 4 times slowly for every 1 time fast. This coda is notorious, so just know that you're not alone! What does your teacher say about it?