Very, very good. If you stick with it, you'll be a player. Like DP says, work your left hand in. To get the part you're having trouble with, go very slowly on it and gradually work up speed. Chris Miller, Wilson Savoy, and many others have told me: If you want to go fast, you have to go slow; or as Chris says, you have to take your medicine! 'Course, Balfa Camp would be a good idea . . .
You are off to a very good start. You need to learn your octave notes, but that will come. Go to Big Nick Box lesson. http://www.bignick.net/BoxLessons/boxlesson_Index.htm There are some basic lessons for free on how to play Cajun Accordion. There is also a link for The Back Door. When you get to the Back Door page scroll down to the bottom of the page and click on next page. There you will find videos of how to play Back Door. This is how I learned the tune. Good luck and keep squeezin'.