I would have to respond that as far as I know, the RAW are completely unclear on this matter.

But how I rule on that is kind of tangential to my main point, so perhaps I made a mistake in trying to illustrate my argument with the process by which we decide this question for the claws.
Again, my key assertion is that a numeric range is not, in itself, a variable numeric effect. With fireball, flaming sphere, or wall of fire, the numeric range given has to be considered a property of the spell itself, since none of these things exist outside the framework of that particular spell. The spell itself is dealing damage.
But when the spell creates a weapon, the damage range is a property of that weapon, not the spell. When you attack someone with the claw, it is simply not the spell dealing damage, it is the claw itself. I don't think this is an arbitrary distinction.
(For what it's worth, I don't think considering the power/spell resistance of a spell is useful in determining whether it is empowerable or not.)