The magnetic circle is closed with the plate you have mounted on your phone. So there is no harm to your phone.
Keep in mind that speakers also have permanent magnets inside which also do not effect the phone.
Data these days is not stored anymore in a magnetic way, so you dont have to worry about data loss by your phone mount.
I don’t think so, as it’s not running on AC there should be no interference with any magnetic field. At least from the electrical side. If there’s any magnetic material in the battery (the electrodes? but they should be made from graphite, which is not magnetic, I believe, as is the polymer used as the electrolyte) then there may be some effect, but not a concerning one (or one that has an effect), it should be a weaker mechanic force than shaking your phone…