I play stringed instruments so I'm not sure if this applies to accordion players but practice loud. You can always get quieter but it's not so easy to increase volume comfortably when playing with other people. It will also increase your dynamic range and will give you an idea of what your instrument is capable of.

As for anchoring the pinky my philosophy is to be flexible. Most of the time now I don't anchor but occasionally, when I do old time fingerpicking or country blues, I drop the pinky on to the top to help get a heavy back beat.