Thanks for trying our game! Regarding your suggestions:
We wanted to make the in between waves a safe place for the player to think about what upgrades to buy and to prepare the holes for the next wave.
The shovel depth has an explaination in the tutorial. We didn't really know where else to put them, since they follow a patern("can dig <attribute> holes").
I think that while a wave counter would be a good idea, it has the potential to make the game too easy. You can just remember the critical waves and buy the necessary upgrades.
We chose to have generous hitboxes, in order to not make the player feel cheated if the character barely misses it.