To what extend should I keep doing useless stuff with my friends?
You are not causing suffering to others. They cause their own suffering if they want you to get drunk with them &amp; you refuse. You should always have metta (friendship) towards old friends but this does not mean you engage in unwholesome actions with them. 

Also get rid of this condescending attitude you have compassion for your friends and wish to help them. This is disgusting. Your friends are merely “ordinary people” who live ordinary worldly life.

As for your girlfriend, it is love &amp; respect for her that you watch TV with her. It is only TV. You don’t have to attach or delight in what you are watching yet this should not stop you showing warmth and companionship towards your girlfriend. 

I am typing this on an airplane because I am visiting my mother &amp; sister. I watch TV with them even though I do not watch TV at home.  Watching TV can be a meditation upon the ignorance of the world.