It could be the PTSD, wanting to be happy, but afraid to be happy, wanting love, but afraid to love etc. The anger can be from the frustration of the conflicting feelings too. He needs to be in therapy, otherwise, he will begin to lean on you for that and you have enough of your own challenges.

Much also depends on his history too, he could be borderline and that requires therapy from a therapist that can actually help with that challenge.