The correct answers are I abducted fewer cows than I originally planned and Earth has a massive amount of water on its surface.

Quantifiers must match whether a noun is countable or uncountable!

• Fewer is used with plural countable nouns (cows).

• Amount of is used with uncountable nouns (water).

• Traffic is uncountable, so it needs "much," not "many."

• Problems is a plural countable noun, so it needs "a few," not "a little" (which is for uncountable nouns).