misty and instructional breakdown

This Allen Hanlon arr. of this tune was the very 1st chord melody I learned at the tender age of 17 . .In my haste to get this done, (haste never works so well for me . . ruk-ruk), during the breakdown section, I neglect to notice my bad intonation . .grrr! Maybe someone would be good enough to tell me what I can do better, to make an easier to learn format for these 'chord melody how to's'.