When I read your message, I remembered something I heard about people who are abused as children: "they have a hole in their soul".
This is the emptiness he is talking about. It also sounds like he is suffering from depression.
Going into therapy to heal those deep wounds is going to hurt like hell - intuitively, he knows this - that's why he cancels his appointments. What's really sad is that things are just going to get worse and worse until the pain gets too terrible for him to bear.
He needs serious and extensive professional assistance to help him heal the deep emotional torture that was inflicted on him as a child. A support group like Al-anon or ACA would also be helpful.
Prayers and blessings to you and him