Dear saa there is no obligation to keep up with this thread in any particular way. Oma is right, you don't need to be so hard on yourself.
I spent some time praying and meditating today and I got once again what I call my big stick message. Put the stick down and stop beating my back with it, keep loving my DC and keep doing just what I am doing. Tara Brach calls it the second arrowing - the first arrow is the pain and hurt which causes you to act out in some way (by being hostile, or abusing drink or drugs or anything else). That is part of the human condition- but the second arrowing is the arrow you add yourself because you feel bad and hate yourself for the way you act to the first arrow.
Whereas you need to look underneath the pain of the first arrowing and think what does this part of me need? It will be comfort, love, support, any of these positive things, not anger or hate. So, when I imagine what that part of me needs, it is to be held in God's love and I visualise that. God always looks the same in my vision, but maybe it is one of His Angels, I don't know. But it is that point, to not keep fighting or pushing away the bad feelings, but think what they need. Love and acceptance could help.
As regards your DP, I think this is his struggle to get through and I am sorry he is in such internal pain; you cannot answer his questions, just be there and be present with him, not apologising. Little things - a hug, a walk, day to day little things which won't undo the hurt, but which are putting him in touch with God's world. Because whatever has happened, there is still absolute beauty in the world if we open our eyes to see it but he needs to work through the fog bit by bit. And Oma is right, God's love is beyond our understanding and capacity to know, and therefore some questions we cannot answer, only come to terms with. I am praying for you both.