Screenwriting : subplots and B stories by Les Collins

I have a main character pursuing an outward goal. He is separated from his spouse due to a former tragedy. I want to have a slow return to the marriage without taking over the A story. Should this be developed as a B story or a subplot along with the others involving friends and family? there is also a crime element that develops out of the A story. The spouse is not directly involved in the A story and they are separated which makes it hard to involve the main character in her life very much. Any suggestions on how to handle these secondary threads of love interest and law enforcement in this case?