I understand your dilemna Daisy-I've been anguishing over letting scumbag know about our son-but someone has said to me, if he wants his dad to know, then he will tell him, himself.
I know it's different for you, as your gran can't do that, but I do agree with the others. You have come such a long way. Stay strong and put your energy into looking out for your other family members. Your support network has to change and develop as your stbx isn't a part of your future.
Thinking of you xxx