before your ent_bonerotate you need to reset the bone before you rotate it otherwise it will just continually add the value every frame. Im guessing nothing is happening or its going all crazy.
you'de be amazed how useful the manuel can be. press F1 in script editor.
// Bonebewegung für Bogen
camera_tilt = bone_ang.tilt;
camera_tilt = clamp(camera_tilt,-80,80);
bone_ang.tilt = -(pointer.y - 400) / 10; // maybe this needs
bone_ang.tilt = clamp(bone_ang.tilt, -80,80); //re evaluation?
bone_ang.roll = 0; // not sure, i cant exactly test this
ent_bonereset(my,"Bip01_Spine1");
ent_bonerotate(my,"Bip01_Spine1", bone_ang);
my.moveMode = punch;