That's not how you stack boosts. You're increasing Tyranitar's Special Defense directly, not the base stat. And even then, following your logic, it'd be 100 SpD x 1.5 Sandstorm x 1.5 Assault Vest = 225 SpD, which it isn't mind you:
Shuckle's Base SpD is 230, which translates to 496 uninvested...