I think you should tackle the grief first, and maybe the DP is a symptom (what I think of as One Step Beyond, the Madness song, where we go mad away from original cause).
I think grief counselling would be something that could really help, so I hope you'll look into it. If you cant, there's a book called The Grief Recovery Handbook. I know there's no easy answers, but if you have support and someone to talk to it will make a difference.
