My DD7 was having big time abandonment nightmares while my fWH was 'away'. Same thing as your DS. She is in trouble; she calls for daddy to help her; daddy doesn't show. It is the worst feeling in the world to have to watch your child go through the emotional trauma that an A brings into their lives.
IC has really helped DD work through some of her issues and my fWH is trying really hard to make sure he is there for her NOW. She still has issues though. She refuses to go to bed unless I'm in the house. Hell, she still fights going to sleep at night (fWH's MO was to leave after she went to sleep). Her IC said it will take years to overcome and that is the truly sad part; because of my fWH's 7 months of stupidity by DD will be in therapy for years to come.
I suggest getting your DS into therapy as soon as possible. He needs a safe environment to work through what he is feeling.