I come from Hindu background, and I live with my Hindu family. I do not have means to move away. I am feeling very overwhelmed after I found out my family is najis.

I have clean prayer clothes. My other clothes, are always touched by my family when they are hanging to dry. I have a clean towel, but sometimes after my shower, my hair touches impurity.And to get out of shower, I inevitably touch something thats mutanajis.
The whole house almost, at some point was touched with wetness.

Where does the law of difficulty apply and where does it not? I have a hard time knowing what I should care about and what I should not.

May Allah help you through this

The Law of Difficulty applies when it becomes unbearable for you to always maintain your purity. So here’s what I recommend:

1- Keep a set of pure clothes for prayer. Pray only in those clothes.

2- Before you pray just wash your hands and arms and face and feet and then dry your feet quickly with paper towels.

That’s it. Don’t worry about anything else, such as your hair or other body parts being najes. Just assume them to be pure