Thanks for playing and comments!
Yes, Grandfather's ax is an item of imbalance. But this is random. You can find it at the beginning and the game will be easier, or you can find it at the end when it is almost useless. The store tried to inflate the price for it.
And yes, the battle is a simulator of randomization and receiving rewards, so that in the future it will be easier. Perhaps there are options to diversify this phase of the battle, but I didn’t have enough time for it.