1- There are good jinn and bad jinn. Yes, the deviant jinn might be more, just like deviant humans are more. Most people historically have followed the wrong path.
2- Jinns are not more powerful than humans. In fact, humans have a higher capacity for intellect and spirituality.
3- Before Islam, Jinns had more influence on humans. They would interfere more. After the revelation of Qur’an, Allah limited their interaction with humans.
4- Jinns can sometimes harm humans, but they cannot possess them such that humans lose their free will. We have Du’as and A’mal to protect us from evil Jinn.