WTBH,
Great job with D6, as far as grandma is concerned, she needs a big ol can of whoopass opened up on her.
Please keep an events journal in case this would ever come up as part of a visitation request, I don't know about where you are, but in some state grandparents can sue and get unsupervised visitation, weekend vists, etc.
Also you may want to make sure that if your husban gets visitation that he cannot just dump the girls there when it is his weekend.
Very proud of the way you handled that.