Re: How would I apply music theory to the accordion?
This is the same issue I have had with banjo music, guitar music, polka band music, Irish penny whistle music, Cajun music etc.
Let just say that you can write the correct notation but you cannot notate the "pulse". Those are the subtle pauses, sustains, emphasis, thrills and a host of subtle variations inherent in almost every music style.
Basically you learn to play the music as written, then you listen to the masters and what you are missing becomes obvious.
Or, some folks find it easier to just go straight to copying the masters. It is a personal approach thing, whichever is easiest for the individual.