What you interpret as honesty is actually Manipulation. You approach this person as though he lives life with a normal brain and normal feelings. If anyone would confess this kind of thing to you, you would rightly feel empathetic in response. But you are not talking to a person with a normal brain, you are talking to a disease. It is his disease talking to you and you need to forget what he said. He wants you to feel sorry for him. He is hooking you and you know it because you are allowing your emotions and normal reasoning to overpower objectivity.
Detach from your feelings of empathy. Detach from your strong desire to have the love, kindness, and happy family that you once had. Look within for your strength and if you find it is spent, get to an Al-Anon meeting and borrow some of the strength you find there.