Okay I relooked at everything and I found one reason the spell damage coefficient was off. I forgot that I have 3/3 in piecing ice which is basically a 1.06 damage multiplier.
For determining the base damage I went ahead and attacked mobs while having 0 sp.
Average damage ranges were:
479-516 (avg 497.5)
Since I have 3/3 piecing ice the base damage at 0 spell power will be 497.5/1.06 = 469.3.
The frostbolt spellpower coefficient does actually make a difference when comparing spellpower to hit/crit. If you change the coefficient it changes how important spellpower becomes. I can show why this is true if you are skeptical.
I did some testing at different spellpowers and back calculated a spellpower coefficient of 0.84. Now the difference between using 0.84 and 0814 only changes the ratio by ~0.10 spellpower so It doesn't matter much anyway. I can show how I come up with 0.84 as the coefficient if anyone wants to know, I just don't want to make things confusing.