So, the formula says,

Take the "buildings:tank" ratio, raise it to the power of something, and multiply it by a number that increases slightly per special attack already made. Then if the damage is less than 0.1, set it to 0.1.

So there is no maximum damage that can be done, only a minimum of 0.1.

-------------------------
Without knowing what $exponent is (whether it is larger or smaller than 1), the

pow(ratio,exponent)

where ratio is the adjusted building/tank ratio, can result in just about any number between 0 and infinity.

Let's look at 4 cases from the smallest result to the largest:
ratio < 1, exponent > 1: Result < ratio
ratio < 1, exponent < 1: Result < 1
ratio > 1, exponent < 1: ratio > result > 1
ratio > 1, exponent > 1: Result > ratio

In the extreme case of 0 tanks, you end up with this on the first AB:

max(0.1, [($frontcut)/$divisor] * pow(($target_buildings + $addtop)/$addbottom, $exponent))

If exponent is a large number, that is only going to amplify the very large adjusted building/tank ratio, and you end up with ridiculous returns.