FASA Games, Inc.

Can you use spell like Spirit Grip to inflict Stun Damage rather than kill somebody? Or other damage-inflicting spells?

No, it is a combat option only for close combat. Spells don't have a "flat of the blade" to strike with, nor is there an "on fire, but only for some really wicked heat exhaustion" part of a Fireball to inflict, or the "pillow case of doorknobs" version of Bone Shatter. There is definitely room for spells which are dedicated to inflicting stun damage, but it would directly state this.

It's a hard world