Dad is clueless and his kids need direction. David, is worried and Jon is a shit for calling him a fag and probably knows it hurts. Suzanne has too much to do and maybe needs to get some counseling herself otherwise how will she figure out what to tell her dad.
Dad is drinking way too much for the responsibility he has and for his own health and yes it is now clear he is self-medicating due to his own PTSD. He has most of the symptoms including numbed emotional response, denial, flashbacks, and more from the clues dropped in the last two chapters....