Answer:
The author wants you to see that this rodent was born into a life of hardships and never got to experience a normal life without danger.
a cotton ball is a lifeless ball of fluff, which is how the rodent is treated in this giant city. It is kicked and run over as if it were an object, where the people don't consider the feelings of the rodent.
the tail being described as a toothpick I think represents the life of the rodent, unmoving and painful. The rodent's life will never change, it will keep on experiencing the pain life gives it.
Explanation: