Do Jehovah’s Witnesses have anything in common with the Pharisees? Have they made Jehovah a petty God?

No, the Bible has principles that apply to all things in life. Humans cannot trust their God given conscious to make godly decisions because humans are ungodly by nature of being imperfect and sinful. God is a God of peace and order. His laws and principles, when followed, keep peace and order. 1Corinthians 14:33