I can see keeping [Force] to get the damage to incorporeal undead if you have too. I'd say that positive energy also does full damage to undead even in Pathfinder.

There is still nothing [Good] about the spell. It's just an attack spell. Tell me why fireball is not a [Good] spell? Positive energy is not good, nor is negative energy evil. They can be used for good or evil, but they are not good and evil themselves. Searing Light, for example, is not a [good] spell.

And the spell should be pure necromancy.

And...oh...you have the spell written as an undead harming spell only right? Why? Positive energy harms everything.

And just personal taste, but 'scarabs' are icky bugs associated with death.....I'd rename the spell Bright Bunnies!