you must trust it from the rasp via bluetoothctl for autoreconnection in my remember
and for the audio source option , you should test
pactl load-module module-switch-on-connect.
from marcopi answer , i have not test that command, but i think if it work that would simplify your configuration.
And for your audioheadphone, no solution, maybe some drm or something like that ?
Glad to see that my post is usefull for some other people 