You're missing one ) from the end of your formula. Therefore the formula will error, resulting in a damage of 0. (Additionally, if your game is in XP/VX/Ace, precision in the final part of the formula could be an issue, where 1 - (n / x) will always result in 1 as long as n is less than x, meaning that DEF will not factor in as much as it should - this can be remedied by changing all values to a decimal such as 1.00 instead of 1)
Getting back to preference in formulas, I'm a fan of keeping it simple unless it badly throws off balance. In my last two games, I've used a formula of (ATK * BaseSkillPower) / (DEF + 10) for most skills. This allows the practical effects of changing certain stats to be very transparent to the player. Double your Attack, double your damage. In this line of thought, I was fond of your first formula, rather than the more complicated second or third.
Your formula #1 (and #2) also has what I consider in advantage over #3, in not using any "square powers" (such as "ATK * (ATK / 2)" which cause damage to increase exponentially rather than linearly with level. Since your HP formula does not increase exponentially with level, I worry that your battles will be very difficult to balance at high Levels with any exponential damage formula.
One final thought: I know that you said you've already made up your mind on the third, but the given reasoning was pretty weak. You are somewhat arbitrarily (it seems like) dividing certain numbers by 2, etc., throughout your formula; if the reason you don't like the second formula is that the numbers are universally too low, simply multiply all the damage formulas by 3 or whatever. I'm personally agnostic between #2 and #3,
