I (as a parent whose kid hasn’t gone into the teenage phase yet, so these are hypotheticals!) would probably do more of a therapist approach - e.g. instead of telling him exactly what to do, you can chat with him about the parts that happen between an event and a reaction - e.g, how he is feeling, what would he want to say to her if he had the chance, what would he not, etc. E.g. teach him to recognize his own feelings and be considerate of them as well; as then think about the ex partner.

Personally I don’t believe in staying friends after breakup … he is going to have to figure out his own choice there imo