duh.. off course
My problem with the bumper is "just" applying either velocity or torque (or both) to the player into the direction of the bumpers pan

While writing this, I had another idea and quickly tested it out
if I use

phent_addvelcentral (player, vec_scale(my.pan, 50));

it seems to work more or less. for some reason it only bounces the player away in 3 of 4 impacts

Got no real ideas yet about the two colliding balls problem though.