Hi WAS,

the first chord of a song does not have to be the tonic at all. You can find examples in any kind of music style.
A chord with a sixth ajoutee is in classical music found normally on the IV degree to reenforce the subdominant character. In Jazz the sixth ajoutee is not only used on the subdominant but also on the tonic and even on the minor tonic also.
To end with a Maj Seventh or Major Sixth chord is very comun in Jazz.

By the way, if you just take the second and thrid row of your changes you can recognize a famous standard called "Satin Doll". --->

Dm7 G7 Dm7 G7 Em7 A7 Em7 A7
Am7 D7 Abm7 Db7 CMaj7 F7 Em7 A7


Listen to it here ---> https://www.youtube.com/watch?v=TrytKuC3Z_o