19 can be a tough age .... Not a child yet not a full fledged adult either. children of troubled marriages are not mature enough to understand the dynamics and underlying issues and react to emotions not rationality.
As an Acoa I agree... Give him space and let him know that you love him unconditionally and are sorry to see him in pain...that it's not his fault. Kids are collateral damage when marriages end even for good reason.
I am a strong believer in counseling with the right therapist....sorting it out will help him navigate his own future relationships. Will he consider it?
Time is your friend.... Just keep loving him even when he isn't loving you back.