Would the cook's salary be permissible if he worked in a restaurant that sells beer, but away from him, provided that his salary does not include any part of the alcohol sales or customer tips?

The salary of the questioner is permissible as long as his work is lawful, and the permissibility of the wage is a branch of the permissibility of the benefit. He does not sin by selling permissible food in a place where alcohol is sold, as long as he does not directly engage in anything related to it. It is preferable to abstain from such places out of aversion to evil, but it is not ruled as impermissible due to the absence of direct assistance in selling or consuming alcohol.