Nicola I can so relate to what you are saying. My d5 would come back and talk about ow. She plays barbies with my girls. I know she wants them to like her. I have asked my girls not to talk about her. It really helps my pma. I don't think I should have her name uttered in my presence.
Anyway I find it quite sad that these ow are wanabe parents to our children. Really how pathetic.
I know it is hard but take it one day at a time. Do take the time to grieve your m.
It will get easier. There will come a time when all this is not the first thing you think about when you wake up. There will be a time when you will forget what it was like having h live with you. You will carve out a wonderful new life for yourself and your children. I know it is hard to believe now but just keep moving forward and it will all work out in the end.