Oh, I see what's wrong with your stat math already. you're not using the right formula, the right one is the one I posted. It has no "starting value" as a thing in the formula, but is compensated instead by stuff like levelX5(statgrowth) + constant + etc.
Use that one.
Using "starting growth" as a stat isn't accurate because the starting value gets cheated of the 0.02% bonus gained per level..or something, I'm too lazy, but I'm sure it's something like that, just try it >=P.
I figured it would be something like that, yeah. I'll give it a try later when I've got free time and check it out.
Edit: Okay, messed with it now, and yeah, your formula comes out right on the dot for atk/mag/def/mnd... except for Remilia's ATK, again (but that's closer, this time). To make sure I'm not plugging in numbers wrong...
(Level+4 * Growth Rate + constant{just take their starting value - level statuprate*5 to get it, I think it's normally 3 though}) * (1+0.02(level-1) + 0.02(times selected stat for level up bonus) + 0.04(skill level - 1) + ItemStats)
So, with that hypothetical level 380 Remilia I mentioned above at base stats...
(380+4 * 16 + (69 - (16 * 5))) * (1 + 0.02(380-1) + 0.02(0) + 0.04(1-1) + 0)
Simplify...
(384 * 16 + -11) * (8.58)
6133 * 8.58 = 52621.14
But, for Remilia, I'm getting an in-game total of 51757.
It works 100% perfectly on all the other characters (and all of Remi's other stats), though, as far as I can tell. Also, as for decimals, it seems to truncate them generally, although SP doesn't seem to always follow that behavior.